ESSOINS  ON  THE  EYEl 


.i.;^^. 


M.  B.  KETCHUM,  M.  D. 


UNIV 


OF  THE 


OF 


iXTY 


^FOR^ii 


aZ-^Ul/     ^^^-^i^''-^' 


Ketchum's  Lessons 
ON  THE  Eye 

Dedicated  to  the  "World  of  Optometry"  and 

Especially  to  Those  Who  Have  Sacrificed 

Their  Time  and  Energy  to  the  End 

That  the  Word  "'Qptometrist" 

May    Be    Honored    by    All 

Other  Professions 


the  contents  of  this  book  has  been 
especially  arranged  to  meet  tfie 
present  day  needs  of  the  optometry 
student,  it  covers  the  essentials 
OF  the  "structure  and  function  of 
the  eye,  the  orbit  and  its  appen- 
dages".     ALSO    the   diseases    OF   THE 

eye    that     he    should    recognize 


Edited  and  Published  by 

MARSHALL  B.  KETCHUM,  M.  D. 

President  and  Founder  of  the 
Los  Ans^-eles  Medical  Scliool  of  Oplitlialmolog>'  and  Optometry. 


Los   Angeles.    California. 
19  2  0 


JicluiOli 

fiDtf.raetrists 


a 


RE  51 
K4 

UBRARY 


A  FEW  APHORISMS 

()1'T()Mi^:trv,  today,  is  the  highest  conception 

THAT  those  best  OUALIEIED  TO  KNOW,  THINK 
IT    IS. 

WE  CANNOT  HARMONIZE  OUR  TEACHING  WITH  THE 
student's  capacity  for  LEARNING,  NOR  HIS 
IDEAS  OF   HIS  SPECIAL  REQUIREMENTS. 

DO  NOT  BE  IGNORANT  OF  YOUR  IGNORANCE,  BUT 
KNOW   THAT    YOU    KNOW. 

THE  KNOWLEDGE  OF  OPTOMETRY  MUST  COME  TO 
THE  STUDENT   IN   AN  ORDERLY  WAY. 

ALL  THINGS  ARE  DONE  BY  THOUGHT. 

THE  DIFFERENCE  BETWEEN  THE  OLD-TIME  REFRACT- 
ING OPTICIAN  AND  THE  OLTALIFIED  LTP-TO-DATE 
OPTOMETRIST  IS  EXACTNESS  IN  DETAIL  BASED 
UPON  A  DEEP  KNOWLEDGE  OF  HIS  UNDERTAK- 
ING. 


M67513a 


ANATOMY-iiic; 

ms  STRUCTURE-all  or  any  part 

()!■  1  he  l)0(ly. 

PHYSIOLOGY 

1  uican.FUNCTION.    The  nat- 

physiological]             lual  action  of  any  part 
of  tlic  anatomy  of  the 

l)0(ly    cither    alone    or 

in      eonjiinetion       witl'. 

any   other   i)ait    of   tin' 

body. 

PATHOLOGY 

/  Pertains  to  a  diseased  condition 

PATHOLOGICAL\  of  any  part  of  the  Ixxly. 

ETIOLOGY- 

CAUSE  of  any  fault. 

DIAGNOSIS— 

Recoo'nition    of    the     nature    of 

diseased  conditions. 

PROGNOSIS— 

Jndf>nient  fornu>d  reiiardint>'  th" 

futui'c  outcome  of  a  diseased  con- 

dition. 

Ri:xci-.  r.ooKs  ox  ("<kxi-;r.\l  AxAT()M^   axu  I'lnsioLocv 

Cu  X  X I  X( ;  1 1 A  .\i Morris ( ikw 

Also  Sii-avart'.s  Maxiwl  of  riivsioi.ocv 

.^lA^•  ox  Disf.a.sks  of  thf  1-ai:. 

(iori.i)'s  I'oi  Isi:t  Mi-huaf  Du  tio\  arn'. 

1)i:\\i-.k's  I  h:  \i«  Axi)  \i:(K. 


Ketchum's  Lessons  on  the  Eve 


INTRODUCTORY  REMARKS. 

An  Optometrist: — means,  at  the  present  time,  anyone,  wlio 
having  properly  qualified  for  the  purpose,  has  his  practice 
limited  to  the  diagnosis  and  correction  of  defective  vision  not 
due  to  disease,  as  well  as  abnormal  conditions  of  the  muscles 
of  the  eyes  amenable  to  relief  or  treatment  with  lenses,  prisms 
and  ocular  calisthenics.  Also  the  diagnosis  of  any  patholog- 
ical condition  of  the  eye  that  he  may  refer  the  case  to  the 
Oculist  for  medical  or  surgical  treatment. 

Owing  to  unfamiliarity  with  the  technical  terms  of  regu- 
lar medical  books  on  the  subject  of  anatomy,  physiology  and 
pathology  of  the  eye  and  the  limitations  of  his  professional 
and  legal  requirements  on  these  subjects,  the  student  and 
practitioner  of  Optometry  has,  as  a  class,  been  unable  to  "get 
the  story"  as  he  should  know  it. 

The  Author's  extended  expei'ience  as  an  Oculist,  Professor 
of  Ophthalomology  in  a  Medical  School  for  several  years,  as 
well  as  personally  training  the  Optometrist  from  the  "raw 
into  the  finished  product"  has  given  him  a  rare  insight  into 
the  exact  needs  of  the  non-medical  refractionist  along  these 
special  lines. 

This  book  is  edited  especially  for  him  and  is  entirely  differ- 
ent from  anything  in  print.  It  is  not  only  for  the  student 
who  is  just  enterhig  this  special  field  of  endeavor,  but  for  the 
licensed  Optometrist,  as  well;  and  we  might  add,  that  the 
medical  refractionist  Avill  find  many  features  of  interest  to 
him. 

The  standpoint  from  which  the  subject  matter  is  presented, 
is  that  of  a  fairly  complete  Avorking  knowledge  of  the  eye  and 
its  appendages  and  is  of  sufficient  scope  to  practically  cover 
all  that  the  Optometrist  will  be  required  to  know  of  this 
branch  for  years  to  come. 

In  no  sense  is  the  minute  anatomy  of  the  eye  any  necessary 
part  of  an  Optometrist's  requirements.  He  does  not  cut,  he 
does  not  treat,  as  that  is  the  legal  function  of  the  Ophthalmic 
surgeon,  but  his  knowledge  of  the  eye  is  required  to  be  of 
such  a  nature  that  for  the  good  of  the  patient  as  well  as  him- 
self and  his  professional  associates  he  Avill  be  enabled  to 
follow   his    calling    intelligently    and    know     his     limitations. 


10  Kiyiciu'M's  Li:ss()\s  ox  Jiii-:  Imk 

Three  main  tliin«>s  confront  all  refractionists  when  a  patient 
comes  for  advice,  b'iist,  does  he  need  f>lasses  oidy  .'  Second, 
does  he  need  1  ic;i1  nuMil  as  well  as  <>]ass('s,  and  thii'd,  does  he 
need  trcatiiicnt  only.'  'I'liis  llic  ()i)t()metris1  must  know  and 
tlien  act  accordiiitily.  Miu-li  iiioie  mi^ht  he  said,  Init  we  leave 
that  to  the  student  as  we  \'cr\  sure  tliat  lu'  will  iind  herein 
niucli  of  interest  and  value  to  him. 

1  have  planned,  in  my  endeavor  to  helj)  the  student,  to  make 
this  usually  dry  subject  a  decidedly  interesting  one  to  him. 
First,  by  jiresenting  in  picture  form,  Avith  notes,  a  general 
scheme  in  their  proper  order,  of  the  principal  parts  of  the 
subject  that  he  should  master.  Then  following  Avith  a  talk 
on  each  pai't  sufficiently  explicit  so  that  a  gross  knowledge 
is  methodically  and  easily  gained.  The  quiz  following  each 
lesson  covers  the  essentials  and  causes  the  student  to  care- 
fully review  that  lesson  and  learn  to  foi'mulate  his  own 
answers.  Having  completed  the  general  outline  of  the  Avork 
in  this  manner  \  have  presented  in  Parts  Two  and  Three  undei' 
s])ecial  headings  a  more  intimate  and  comph^te  consideration 
of  the  individual  parts  of  the  eye  that  was  covered  by  the 
lessons,  as  Avell  as  many  other  features. 

^lARSHALL  B.  KETCHUM,  M.  D. 


Ketch  If  m's  Lkssoxs  ox   iiii-:  Evi-:  11 


LESSON  ONE. 

(Section  One.) 

Til  taking  up  tlio  study  of  tlic  eye  it  is  well  for  the  Optometry 
.student  to  realize  that,  Avhile  as  a  class  the  human  eye  is 
pretty  much  the  same  in  all  ])eople,  a  "reat  deal  of  compara- 
tive study  has  been  necessai-y  in  order  to  arrive  at  a  definite 
standard  of  anatomical  and  optical  measurements  and  the 
principles  therein  involved,  so  as  to  form  a  basis  for  considera- 
tion from  all  standpoints;  hence,  the  term  "SCHE^IATIC 
EYE"  has  been  adopted  to  cover  Avhat  may  l)e  considered  as 
the  perfect  eye. 

The  following  figures  are  given  to  convey  at  once  a  gross 
conception  of  the  eyes  and  tlie  orbits,  along  with  the  general 
scheme  of  their  relationship,  and  this  Avill  lead  to  an  interest 
in  the  text  that  follows. 


THE  METRIC  SYSTEM. 

Everyone  should  l)e  familiar  with  the  metric  system  of  meas- 
urements. 

The  inch,  foot,  and  yard  system  is  practically  obsolete  in 
anything  but  gross  work,  though  the  average  person  does  not 
seem  to  know  it.  A  fiftieth  or  a  thousandth  of  an  inch  or  yard 
is  practically  an  indefinite  quantity  and  the  scientific  man  has 
no  use  for  it.  Such  a  system  should  be  entirely  abolished  as 
being  too  crude  for  the  present  day  requirements.  "Decimals 
and  fractions"  is  the  only  definite,  certain,  and  easy  Avay  of 
obtaining  or  properly  explaining  any  weight  or  measure  that 
requires  delicate  consideration.  The  importance  of  possessing 
a  uniform  system  of  measures  that  is  su]).ject  to  infinite  and 
exact  consideration  has  been  recognized  by  scientists  generally 
for  some  time  past.  In  Eui-ope  it  is  pi'actically  the  only  method 
in  use.     It  is  called 


Kktciium's  Lessons  ox  tiil:  Eve 


The  Metric  System  and  in  calculalioii  corresponds  Avith  the 
Avay  we  fiourc  dolhirs  aud  cents.  Jt  is  founded  on  the  Avord 
metre,  wliich  is  the  unit  of  length,  based  on  the  measuroinen, 
of  llic  iiuadrant  of  a  meridian  of  the  earth.  There  are  only 
three  parts  of  this  system  that  we  usually  use  in  our  ordinary 
ophllialniic  and  optical  nieasui'cnicnts.  They  are — ^Feti'e. 
Centi-nietre,  INIilli-metre.  Study  this  table  a  few  minutes  and 
you  will  have  it.  The  Optical  houses  furnish  small  ivory  rules 
and  caids  showing  by  measure  exactly,  centi-metres  and  milli- 
metres as  compared  with  the  inch  system. 


IMetre  Centi-metres 

1  =  TOO 


!^^illi-metres 
1000 


Explanation — The  smallest  decimal  we  use  is  1  niillini-.'tre 
(mm.)  and  it  takes  10  nun.  to  make  1  centimetre  (cm.) 
and  that's  all  there  is  to  it.  (^onipaied  with  the  inch  system, 
the  optical  student  should  be  able  to  transpose  from  one  to  the 
other.  It  is  as  follows :  1  m.  =  about  40  inches  (1  yard  and  4 
Inches.)  25  mm.  =  about  1  inch.  If  10  mm.  =  1  cm.,  then 
it  would  take  2:-')  em.  to  make  2.1  mm.  or  1  inch. 

In  all  optical  problems  these  ivlative  measures  are  used. 
Kclalive  to  the  dollar  system,  it  is  like  this:  1  meter  =  1  dol- 
lar; 1  centinieti'e  =  1  cent;  1  mm.  =  1/10  of  a  cent.  Now 
looking  at  a  rule  with  millimcties  ami  centimetres. marked  oflf 
on  it  yon  Avill  become  familiar  by  sight  just  what  each  one  is 
as  to  dislanee.    Here  it  is. 


Inch  System 


Metric  System 


Ketchum's  Lessons  on  the  Eye  13 


Figure  1. 


Every  normal  person  has  two  eyes,  (either,  being  a  perfect 
mate  for  its  fellow  eye)  so  situated  in  their  respective  posi- 
tions in  the  head  as  to  be  parallel  one  with  the  other  and 
under  such  control  of  the  eye  muscles  as  to  Avork  and  move 
together  in  perfect  relationship  when  looking  at  objects  at 
any  and  all  distances. 

They  are  located  in  the  upper  and  front  part  of  the  skull, 
each  in  a  bony  cavity  commonly  called  the  orbit  (eye  socket). 

The  distance  between  the  two  eyes  varies  somcAvhat  in  dif- 
ferent individuals,  OAving  to  the  fact  that  the  general  measure- 
ments of  any  tAVO  heads  are  not  identical.  HoAvever,  in  the 
average  adult,  Ave  usually  find  that  from  the  center  of  one 
pupil  to  the  center  of  the  pupil  of  the  other  eye,  (called  pupil- 
lary distance — abbreviated  P.  D  .)  it  is  about  60  millimetres, 
while  the  average  range  of  distance  betAveen  the  eyes  is  from 
56  mm.  (214  inches)  to  60  mm.   (21/2  inches). 


14 


^oxs  ox   liii'; 


Figure  2 


Figure  2  is  to  illustrate  the  fact  that  although  the  two  eyes  are 
];arallel  the  two  orbits  are  not  i)arallel,  but  diverge  from  one  another; 
also  that  in  front  (the  base)  they  are  somewhat  oblong  and  irreguhir  in 
form  and  droop  downward. 


Kktchum's  Lessons  ox  tiik  J'Lve 


15 


Figure  3 


Figure  3  is  to  sliow  tlie  position  of  the  orbits  and  how  the  ej-es  lie 
in  each  orbit  and  are  held  in  a  position  of  parallelism  by  the  muscles 
that  control  their  action.  See  also  how  they  are  connected  with  one 
another  where  the  optic  nerves  join,  inside  of  the  skull,  and  connect 
with  the  brain. 


16 


Ketciilm's  Lessoxs  ox 


HE  E^ 


A' J-  r.f. 


Figure  4  shows  front  view  of  the  right  eye  in  the  orl)it  and  how  the 
muscles  hold  it  in  its  proper  position  straight  ahead,  and  thes:e  muscles 
are  so  arranged  that  the  eye  can  be  moved  in  any  direction  with  the 
slightest  effort. 


Kktciium's  Lessons  on  Tiiii  Eve 


17 


Figure  5 


Figure  5  shows  the  eye  surrounded  by  a  soft  cushion  of  fat  which 
offers  no  resistance  to  its  movements  in  any  direction.  It  also  acts  as 
a  support  to  the  eye. 


18 


Ki:tciium's  Li:ssoxs  ox  tiik  Eve 


Orbicularis  oculi 


Rectus 
superior 


Levator  palpebr^ 

bUPERIORIS 


Figure  6 


Figure  6  shows  a  view  of  the  right  eye  from  above — top  of  skull 
removed.  The  position  of  the  e.ye-ball  within  the  orbit  along  with  the 
arrangement  of  some  of  the  muscles  that  control  its  movements. 


Ketchum's  Lessons  on  the  Eve 


19 


Obliqut-S  superior 

\  Levator  palpebre  superioris  (cut) 

^  Rectls  superior 

Rectus  lateralis 


Obliquus  inferior  Rectus  inferior 

Figure  7 


Figure  7  sliows  side  view  of  eye  and  muscles  which  gives  an  idea 
how  the  eye-ball  lies  within  the  orbit. 


20  Kktciilm's  Lessons  ox  thf,  Eyk 

The  net  of  S(>oiiig  distinctly  is  a  peculiar  one  and  involves 
many  tine  points  for  consideration.  Figure  8  is  a  sketch 
made  to  illustrate  the  fact  that  the  eye  alone  is  practically 
only  a  medium  through  Avhich  vil)rations  of  light  coming  from 
some  object  outside  of  the  eye  are  properly  adjusted  -svithin 
it.  These  visual  sensations  are  then  conducted  on  through 
the  optic  nerve,  to  Avhere  it  joins  the  optic  nerve  of  the 
fellow  eye  at  the  optic  chaism  (O.C.),  where  all  points  are 
fused  together,  and  from  there  on  through  the  right  and  left 
optic  tracts  to  different  lobes  of  the  brain  where  the  "sense 
of  sight"  is  located.  The  diagram  shows  hoAv  the  correspond- 
ing sides  of  the  retina  are  united — at  the  optic  chaism — by 
crossed  fibres  and  accounts  for  the  "field  of  vision"  in  each 
eye  and  that  objects  seen  with  both  eyes  are  united  where 
the  optic  nerves  meet,  the  fibres  on  the  right  side  of  both 
nerves  uniting  thei'c,  and  after  union  going  thence  into  the 
brain  in  the  nerve  Mhich  is  on  the  right  side  of  the  head,  and 
the  fibres  on  the  left  side  of  both  nerves  uniting  in  the  same 
place,  and  after  union  going  into  the  brain  in  the  nerve  which 
is  on  the  left  side  of  the  head,  and  these  tAvo  nerves  meeting 
in  the  brain  in  such  a  manner  that  their  fibres  make  but  one 
entire  species  of  picture,  half  of  Avhich  in  the  right  side  of 
the  sensoriuni  comes  from  the  right  side  of  both  eyes  through 
the  right  side  of  both  optic  nerves  to  the  place  Avhere  the 
nerves  meet,  and  from  thence  on  the  right  side  of  the  head 
into  the  brain,  and  the  other  half  on  the  left  side  of  the  sensor- 
iuni comes  in  like  niannci'  from  the  left  side  of  both  e\es. 


HEREDITY. 

The  influence  of  heredity  on  the  eye  and  its  appendages  is 
particularly  noticeable  in  a  great  many  families,  as  recent 
studies  show  more  and  more  the  tendency  of  the  offspring  in 
many  Avays  to  i'eseml)ie  the  parents  even  in  the  most  minute 
details  of  structure  and  this  fact  deserves  careful  considera- 
tion as  this  subject  has  not  been  giA-en  tln^  critical  stutly  tliat 
it  deserves. 

At  birth  the  two  liuinan  exfs  do  not  woi-k  in  perfect  har- 
mony togetlicr.  .Mi'aniiig  that  the  inlliieiice  ol'  the  action  of 
the  muscles  1lia1  liohl  each  one  in  ])osition,  is  not  inider  any 
kind  of  conlnil,  j)liysiologically  sj)eaking,  at  this  time;  so  that 
the  infant  iiia\,  \-ery  early  in  life,  look  more  or  less  cross-eyed 
nntil  tlie  iicecssity  for  binocular  fixation  comes  into  pla\.  In 
llie  eoiiisr  of  from  si.\  iiioiiUis  to  a  veai',  as  the  e\('sii>jit  (level- 


Figure 
For  description  see  page  20. 


Ketchum's  Lessons  ox  the  Eve  21 

opes  along  with  the  slowly  growing  intellect  of  the  child  it  be- 
gins to  take  notice  of  moving  objects  and  directs  its  eyes  to- 
Avard  them,  and  thus  in  the  course  of  time  he  learns  by  experi- 
ence to  judge  the  distance  and  locality  of  an  object  as  Avell  as 
its  physical  characteristics.  Seeing  the  same  object  with  both 
eyes  at  the  same  time  demands  certain  adjustments  of  the  ])osi- 
tion  of  each  eye  in  relation  to  one  another  in  order  that  at  all 
times  and  all  positions  and  distances  by  perfect  fusion  the  two 
images  become  as  one.  This  is  a  physiological  function  Avhich 
Avhen  fully  developed  is  called  the  Fusion  Power.  As  a  rule 
this  fusion  power  is  not  completely  developed  until  the  end  of 
the  sixth  year. 


22  Kktciium's  Lessoxs  on  tiii-:  Eve 

LESSON  ONE. 
(Section  Two.) 
THE  ORBIT. 

The  orbit  is  the  first  to  be  considei'ed  l)ecaiis(>  it  serves  as  a 
protection  for  the  eye  which  is  imbeded  Avithiu  it  in  a  l)ody  of 
fat,  this  fat,  hoAvever,  offers  no  resistance  to  the  movement  of 
the  eye  in  any  direction. 

It  is  rather  cone  shaped  with  its  base  forward  and  the  apex 
extending:  backward  and  inward  at  an  angle  of  abont  40  de- 
grees with  the  median  plane,  straight  ahead. 

Tts  average  dimensions  are : 

Depth  abont  45  millimeters. 
Horizontal  (at  base)  about  40  mm. 
Vertical  (at  base)  about  35  mm. 

It  has  four  sides,  four  angles  and  nine  openings,  each  open- 
ing is  called  a  foi'amen;  plural,  foramina. 

Kaeli  orbit  consists  of  seven  ])oiies  wliieh  arc  located  as  fol- 
lows : 

Roof  (al)ove)     1.     Frontal. 

Floor  ())elow)   2.     Superior  INlaxillary. 
:j.     Palate. 

Nasal  side  4.     Ethmoid. 

5.     Faehrynial. 

Tomi)()ral  side   (i.      Sphenoid. 
7.     Malai-. 

As  llu'ce  of  Ihcsc  hones  serve  1o  I'oiin  a  part  of  t>aeli  oil)i1, 
viz.:  Ihi'  ffonlal,  elliinoid  and  sitheiioid.  i1  ivquiivs  only  eleven 
sep;ii';i1e  bones  to  forni  holli  orhils.  \o1  all  of  each  bone  is 
iiMpiired  1o  form  the  oihit,  bnt  onl\  vliat  is  called  the  '■orbital 
])oi-tion"  or  i)art  of  tlu'se  l)ones.  otherwise  they  go  tt)  nnd^e  np 
Die  skull. 


1. 

Supra-orbital, 

2. 

3. 

Anterior-ethmoidal, 

4. 

5. 

Malar, 

6. 

7. 

Spheno-niaxillary  fissure. 

8. 

9. 

Sphenoidal  fissure. 

Ketciium's  Lessons  on  the  Eye  23 

The  walls  of  the  orbit  as  a  Avhole  fonn  a  strontf,  bony,  ring, 
at  its  base,  called  the  Orbital  Margin. 

The  four  boundaries  or  walls  make  four  angles,  viz.: 

Superior  External  Angle. 
Superior  Internal  Angle. 
Inferior  External  Angle. 
Inferior  Internal  Angle. 

The  folloAving  are  the  nine  Foramina,  viz. : 

Iiifra-orbital, 
Posterior-ethmoidal, 
Xasal  canal  or  groove, 
Optic  foramen. 


Of  these  nine  openings  only  two  concern  the  Optometrisi 
to  any  extent  and  those  are  No.  8  and  No.  9,  because  of  the 
nerve"  and  blood  supply  that  enter  the  orbit  through  them. 

The  Optic  Foramen  is  a  small,  round  opening  at  the  back 
part  or  apex  of  the  orbit,  through  which  the  optic  nerve  and 
the  ophthalmic  artery  enter  the  orl)ital  cavity  from  tbe  inside 
of  the  skull,  while  the 

Sphenoidal  Fissure,  a  much  larger  opening  on  the  temporal 
side  of  the  orbit  serves  as  a  passageway  for  the  nerves,  arteries 
and  veins,  viz.:  The  third,  fourth  and  sixth  cranial  nerves; 
the  frontal  lachrymal  and  nasal  branches  of  the  ophthalmic 
or  first  division  of  the  fifth  nerve,  branches  of  the  sympathetic 
nerve,  the  ophthalmic  veins  and  also  lachrymal  meningeal 
arteries. 

The  BLOOD  SUPPLY  of  the  eye  comes  from  the  ophthalmic 
artery,  (a  branch  of  the  interna!  carotid).  See  Part  Two  for 
particulars. 


Kktciium's  Lessons  ox  the  Eye 


QUIZ  ON  LESSON  ONE  (Section  One). 

1.  AVhat  is  iiicant  by  tlic  Icnii  "schematic  eye"? 

2.  Give  averag-c  P.  D.  lueasuronient.     Use  metric  system. 

3.  What  holds  the  eyes  parallel  with  one  another? 

4.  Are  the  two  orl)its  parallel,  divergent  or  convergent  with 

one  another  in  front? 

5.  How   and   whei'c   are   the   two   eyes   connected   with   one 

another  ? 

6.  What  is  the  cnshion  of  fat  in  the  ()rl)ital  cavity  for? 

7.  Are  the  optic  tracts  in  the  brain  or  in  the  eye? 

8.  Study  the  diagram  showing  the  working  of  the  field  of 

vision  of  both  eyes  together. 

9.  At  what  period  of  life  is  the  fusion  power  fully  developed  ^ 


QUIZ  ON  LESSON  ONE  (Section  Two). 

10.  Describe  shape,  position,  and  dimensions  of  the  orbit. 

11.  HoAV  many  degrees  do  the  orbits  diverge  from  the  median 

line  ? 

12.  How  many  bones  comprise  each  orl)it? 

13.  How  many  bones  are  required  to  foi'm  both  orbits? 

14.  Name  and  locate  the  seven  bones. 

15.  Why  is  it  that  oidy  eleven  l)ones  comprise  l)oth  orl)its? 

16.  Name  the  four  orl)ital  angles. 

17.  HoAV  many  foramina   in   llie  orl)i1  .' 

18.  Describe  Ihe  ()i)lic  foranu'ii  and  tlie  s])luMU)idal  tissure  and 

state  why  lliey  are  especially  nuuitioned. 
1<>.     AVhal   aitery  su])])lies  l)lood  to  the  orl)ital   cavity? 

:\lal<e  vdur  aiisweis  bolli  oial  and  written.  Wi'ilten  answers 
are  niueii  llw  besi  as  then  you  ean  vvi'ry  to  the  text  to  see  it" 
vou  are  right. 


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CENTRAL  ARTERY 
OF  RETINA 


Horizontal  Section  of  the  Eyeball.     Magnified  about  314  X. 


The  student  must  realize  that  this  picture  shows  a  half  section  cut 
through  the  center  of  the  eyei  horizontally  in  order  to  show  the  inside 
parts,  thus  making'  the  lens  look  oblong.  Viewed  from  the  front  the 
lens  has  the  form  of  a  trial  case  double  convex  lens. 


Ketchum's  Lessons  on  the  Eve  25 


TO   THE   STUDENT 

At  this  point,  as  you  are  about  to  study  tho 
eye-l)all,  muscles,  eyelids,  etc.,  he  sure  to  look  at 
some  person's  eyes  as  you  have  never  done  l)efore. 
See  the  lids  as  they  open  and  close.  Notice  how  the 
lashes  turn  up  or  down.  See  the  size  of  the  eye,  its 
color,  how  the  pupil  Avill  contract  and  dilate,  how 
the  muscles  move  the  eye  in  diffei'ent  directions  and 
the  other  eye  follows  it.  As  you  take  up  each  chap- 
ter in  study,  look  at  the  eyes  again  and  again  for 
reference.  In  Part  Two  you  will  find  a  special 
reference  to  each  part  of  the  eye,  going-  more  into 
detail.  Memorize  Part  One  first,  then  go  for  Part 
Tv/o  good  and  strong. 


20  Ketciium"s  Lessons  ox  the  Eve 

LESSON  TWO. 

THE  EYE-BALL. 

This  lesson  is  inercly  a  j>eneral  outline  of  the  eye-1)all  and 
is  intended  to  convey  to  the  stndent  snflicient  l^iiowleduc  to 
serve  as  a  working  basis  for  that  which  is  most  essential  to 
him  at  this  stage  of  his  work,  so  that  he  can  at  once  proceed 
to  take  np  the  study  of  Ophthalmic  Optics  and  have  a  clear 
conception  of  what  li(>  is  doing. 

The  eye-ball  at  birth  is  small  and  nearly  ronnd,  although  it 
varies  consideral)ly  in  size  as  well  as  in  form.  Its  average 
antero-posterior  diameter  is  17.3  mm.,  which  is  much  less 
than  when  it  is  fully  developed  later  in  life.  The  period  of  its 
most  rapid  growth  is  during  the  first  years  in  life;  this  is 
followed  by  a  period  of  slower  growth,  although  the  eye-l)all 
steadily  increases  in  size  up  to  the  age  of  puberty,  and  when 
fully  developed  measures  about  24  mm.  in  its  antero-posterior 
diameter  and  about  23  mm.  in  its  transverse  diameter  at  its 
equator. 

It  is  sometimes  called  the  globe  l:)ecauso  H  is  so  n(\n'ly  round, 
and  has  three  coats  or  tunics,  viz. : 

Name.  Part  of  each  coat. 

1.  External.         Sclerotic  and  Cornc^a. 

2.  Middle.  Choroid,  ( 'iliary  llody  and  Iris. 

3.  Internal.  Retina. 

The  Sclerotic,  commonly  called  the  'Sxliitc  of  the  eye"  is  a 
heavy  fibi'ous  o])a(iuc  nicnibrane  and  eovcM's  the  postcrioi'  tive- 
sixths  of  the  ball. 

The  Cornea  is  the  clear  transi)ar('n1  seel  ion  in  front  and  eov- 
ei's  1h('  anterior  one-sixth. 

The  Choroid  is  a  Ihin  layer  of  brown  ])ignicn1,  nerves  and 
blood  \cs.scls  and  lies  close  lo  1he  schM'ot  ic,  lining  il   enlirel.v. 

The  Iris  is  seen  in  Ihe  fronl  part  ol'  ill."  eye  diit'ctly  haek  ot 
the  cornea.  It  has  an  ojxMiing  near  its  eenter,  (usually  a  little 
to  the  nasal  side),  called  the  pupil. 


Ketch um's  Lessons  ox  the  Eve  27 

The  Ciliary  Body  is  back  of  and  eonliiiuous  willi  llic  iris,  l)ut 
cannot  be  seen  from  the  front.  It  is  e()iu])ose(l  of  two  ))aits-- 
the  ciliary  muscle  and  the  ciliary  processes.  The  ciliary  mus- 
cle is  called  the  "muscle  of  accommodation"  because  it  aids  in 
adjusting  the  focusing  power — the  lens — of  the  eye.  The  en- 
tire second  tunic  is  also  called  the  vascular  coat,  owing  to  its 
many  blood  vessels ;  another  name  is  the  uveal  tract,  an  old- 
time  term  given  to  it  owing  to  a  section  of  the  ciliary  body 
having  somewhat  the  shape  of  a  l)unch  of  grapes. 

The  Retina  is  a  very  thin  transparent  membrane  contain- 
ing arteries  and  veins,  and  lines  the  choroid.  It  is  the  layer 
that  receives  the  outside  images  and  pictures  them  upon  the 
brain  through  the  optic  nerve  which  enters  the  back  part  of 
the  eye  a  little  to  the  nasal  side  of  its  posterior  jDole  or  axis. 
The  exact  point  upon  the  retina  where  all  images  are  actually 
focused  is  located  practically  in  the  center  of  the  retina  and 
is  called  the  macula  lutea  or  yellow  spot,  (usually  called  the 
macula). 

Directly  in  the  center  of  the  macula  is  the  principal  focal 
point  of  the  eye,  called  the  fovea  centralis  or  center  of  focus. 

Within  the  coats  of  the  eye  Ave  find — see  diagram — spaces 
filled  with  fluids;  the  crystalline  lens,  etc.,  which  may  be  de- 
scribed as  follows,  viz. : 


There  are  three  chambers  in  the  eye : 

Anterior,  Posterior,  Vitreous. 

The  anterior  and  posterior  chambers  are  between  the  cornea 
and  the  lens,  being  separated  by  the  iris  but  still  connected  l)y 
the  pupil.  They  are  called  anterior  and  i5osterior  because  one 
is  in  front  of  and  the  other  directly  back  of  the  iris. 

These  tAvo  chambers,  being  connected,  aic  tilled  with  a 
transparent  watery  fluid  called  the  aqueous  humor. 

The  larger  chamber,  l)ack  of  the  lens,  is  tln^  vitreous  cham- 
ber, also  called  the  hyaloid  cavity.  This  chamber  is  lilled 
witli  a  heavy,  thick,  transparent  body  called  the  .vitreous 
humor.  It  somew^hat  resembles  the  white  of  an  egg  in  its  con- 
sistency and  serves  as  a  support  to  the  tunics  or  coats  of  the 
eye  in  order  to  keep  the  ball  in  perfect  shape. 


28  Ki-.TtiirM's  Lessons  ox  tiii-:  Eve 

The  Crystalline  Lens  is  a  double  convex,  transparent,  spher- 
ical body  and  is  a  little  more  convex  behind  than  in  front; 
it  is  located  directly  back  of  the  iris  on  a  line  with  the  pupil 
and  in  contact  with  it.  Its  purpose  is  to  aid  in  focusing 
images  upon  the  macula.  It  is  confined  in  a  very  thin  trans- 
parent membrane,  the  lens  capsule,  and  is  held  in  position  by 
a  delicate  band,  the  suspensory  ligament,  Avhich  (Mitiiely  sui'- 
rounds  it.  This  ligament  is  an  extension  of  the  hyaloid  mem- 
brane, which  is  a  very  thin,  transparent  body  lining  the  entire 
eyeball  adjoining  and  separating  it  from  the  contents  of  the 
large  chamber  which  is  back  of  the  lens. 

All  the  clear,  transparent  parts  of  the  eye,  namely  the  cor- 
nea, a(iueous  humor,  lens  and  vitreous  humor  are,  together 
as  a  whole,  called  the  Refractive  Media,  and  it  is  through  these 
transparent,  refracting  media  that  all  the  images  are  focused 
upon  the  macula. 

The  Optic  Nerve  is  a  long  bundle  of  tibres  coming  from  the 
brain  through  the  optic  foramen  into  the  orbital  cavity  and 
enters  the  posterior  part  of  the  eye  through  the  sclerotic  and 
choroid;  it  then  expands  like  a  cup  in  all  directions,  forming 
the  inner  layer  of  the  retina.  In  looking  into  the  eye  through 
the  pupil  we  see  a  round,  whitish  spot,  apparently  about  the 
size  of  a  ten  cent  piece;  this  is  where  the  optic  nerve  enters 
the  hack  part  of  the  eye  and  is  called  the  optic  disc;  it  is  also 
called  the  "hlind  spot"".  The  optic  nerve  connects  the  eye])all 
with  the  hrain. 


The  Optic  Axis  and  Visual  Line. 

All  imaginary  line.  Hie  central  line  of  llie  globe  dii-ect 
through  the  (•.■i"i1ei'  of  llie  cornea  and  the  lens  to  a  point  near 
tlie   inncf  niai-gin   of  the   macula    is  caUed   tlu'  optic  axis. 

Thei'c  is  a  similar  tefui  called  the  \  isual  axis,  which  is  nor 
llie  optic  axis,  but  is  the  lin.'  of  vision,  visual  line,  and  is  direct 
from  the  fovea  to  tlic  cntci'  of  the  object  look.'d  at.  ca.lled 
tlie  point  of  fixation. 


Ketciium's  Lessons  on  the  Eve  29 


QUIZ  ON  LESSON  TWO. 

1.  What  is  the  size  of  the  eyeball  at  birth? 

2.  What  is  its  size  when  fully  developed? 

3.  Why  is  it  sometimes  called  "the  globe?" 

4.  How  many  tunics?     Name  them. 

5.  Name  the  different  parts  of  each  tunic. 

6.  How  much  of  the  globe  does  the  sclerotic  and  cornea 

each  cover? 

7.  What  color  is  the  choroid? 

8.  Is  the  pupil  in  the  center  of  the  iris? 

9.  What  constitut(^s  the  ciliary  body? 

10.  What  is  the  ciliary  muscle  for? 

11.  What  and  where  is  the  vascular  coat? 

12.  What  part  of  the  eye  receives  images  from  the  outside? 

13.  Name  and  locate  the  exact  center  of  focus. 

14.  Name  and  locate  the  chambers  of  the  eye  and  their  con- 

tents. 

15.  Describe  and  locate  the  crystalline  lens. 
IG.     Where  do  we  find  the  hyaloid  membrane? 

17.  What  constitutes  the  refractive  media? 

18.  Through  what  foramen  does  the   optic  nerve   enter  tlie 

orbit? 

20.  HoAv  can  Ave  see  the  optic  disc :' 

19.  What  connects  the  eyeball  with  the  bi'ain? 

21.  What   is   the    dift'erence   between    optic    axis    and    visual 

line  ? 

22.  Be  sure  to  master  the  metric  system  of  measurements. 


30  Kktciium's  Lessons  ox  the  Eve 

LESSON  THREE. 

THE  EYE  MUSCLES  AND  THEIR  NERVE  SUPPLY. 

Although  the  oibits  diverge  from  one  another,  the  eyes  are 
perfectly  parallel  with  each  other  and  always  move  in  perfecr 
unison.  They  are  enabled  to  do  this  because  each  eye  is  under 
the  perfect  control  of  six  muscles.  Altogether  there  are  seven 
muscles  in  the  orbit ;  the  seventh  one  raises  the  upper  lid. 
These  six  muscles  are  called  the  extrinsic  (meaning  outside) 
muscles.  The  upper  lid  muscle  is  called  the  levator  palpe- 
brarum (meaning  to  lift  the  lid). 

The  Extrinsic  Muscles. 

L     External   Rectus  2.     Internal  Rectus 

3.     Superior  Rectus  4.     Inferior  Rectus 

5.     Superior  Oljlique  G.     Inferior   Oblique 

(The  plural  of  the  word  rectus  is  recti.) 


All  of  the  seven  muscles  have  their  origin  at  the  apex  of  the 
orbit  around  the  optic  foramen  excepting  the  inferior  oblique 
which  has  its  origin  on  the  nasal  side  of  the  floor  at-the  base  of 
the  orbit  in  front.  The  four  recti  muscles  extend  forAvard 
from  the  apex  an  equal  distance  apart  and  are  attached  to  the 
sclerotic  from  6  to  8  mm.  fi'om  the  margin  of  the  cornea.  The 
superior  oblique  muscle  which  also  has  its  origin  at  the  ajiex 
extends  forward  close  to  llic  nasal  side  of  1lie  oibit  to  the 
internal  angle  at  its  base  and  1lien  ihrougli  Ihe  small  tendin- 
ous pulley  called  the  trochlea;  from  there  is  extcMids  obli(|uely 
backwai'd  and  over  the  upper  and  middle  i)art  of  the  eye 
where  it  becomes  attached  to  the  sclerotic  uiidenieatli  the 
supei'ior  rectus  a  little  back  of  the  equator.  The  iiii'erior 
oblifjue  from  its  origin  und(M'  the  nasal  side  of  tlu^  front  of 
the  oibit,  passes  below  the  inferior  rectus  and  turns  u])  on 
the  tempoi-al  side  bet\\-een  the  sclera  and  1h(^  (^xt(M'nal  rectus 
and  is  attached  to  the  seleia  on  its  temporal  side  hack  of  the 
e(pia1oi'  of  1  lie   eye. 


Ketch um's  Lessons  ox  the  Eve  31 

The  Intrinsic  Muscles. 

The  muscles  inside  the  eyeljall  are  called  intrinsic  muscles 
and  are : 

1.  The  ciliary  muscle  or  muscle  of  accommodation 

which  surrounds  the  horder  of  the  lens. 

2.  The    iris    muscles,    circular    and     radiating- ;     1lie 

circular  muscular  fibres — sphincter  pupillae — 
contract  the  pupil  and  the  radiating  fibres  di- 
late the  pupil — dilator  pupillae. 

The  Nerve  Supply 

The  principal  nerves  of  the  eye  that  are  of  interest  to  the 
Optometrist  are  the  third,  fourth  and  sixth  cranial  nerves. 
The  third  nerve,  also  called  the  motor  oculi,  supplies  all  the 
muscles  of  the  orbit  excepting  two;  the  superior  oblique  wliich 
is  controlled  by  the  fourth  nerve  and  the  external  rectus  l)y 
the  sixth  nerve.  Inside  the  eye  the  third  nerve  contracts  the 
ciliary  muscle  and  also  contracts  the  pupil  in  the  iris.  The 
sympathetic  nerve  dilates  the  pupil.  Practically  all  the  con- 
tents of  the  orbit,  the  eyeball,  optic  nerve  and  muscles  are 
enveloped  in  a  fibrous  sheath  called  the  capsule  of  tenon. 


Z2 


Ketciium's  Lkssoxs  ox  the  Eye 


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This  iiiclun  hit  cyo— shows  the  general  arrangement  of  the  con- 
tents of  the  orbit  as  seen  from  above.  Also  the  optic  foramen  and  the 
oi)tic  nerve  passing  through  it,  as  well  as  the  sphenoidal  fissure  show- 
ing a  direct  open  passage  l)etween  the  brain  and  orbital  cavity,  wliich 
serves  as  a  iJassage  for  the  cranial  nerves,  ophthalmic  nerves,  and 
small  arteries. 

The  wide  muscle  at  llic  top  is  the  muscle  tliat  lifts  tlie  lid  -levator 
palpebrarum. 


Ketchum's  Lessons  ox  the  Evi 


33 


a  o 


34  Kktci I um's  Lessons  ox  THE  Eve 

Especial  attention  is  drawn  to  the  superior  oblique  muscle  where 
it  passes  through  the  little  tendinous  ring  called  the  trochlea,  and  from 
there  turns  at  an  angle  backwards  toward  the  eye-ball,  where  it  widens 
out  and  becomes  attached  to  the  sclerotic  a  little  back  of  the  equator 
of  the  globe  underneath  the  sui)erior  rectus. 

It  will  be  seen  that  the  insertion  of  the  inferior  oblique  muscle  is 
on  the  temporal  side  and  somewhat  farther  back  from  that  of  the 
superior  oblique.  These  two  muscles  are  classed  as  the  rotary  muscles 
whose  principal  function  is  to  rotate  or  turn  the  eye  on  its  axis.  Note 
the  shape  of  the  superior  rectus.  Small  at  its  origin,  becomes  wider, 
then  narrow,  and  again  wider  in  order  toi  form  a  broad  surface  of  at 
least  10  mm.  where  it  is  attached  to  the  sclera  in  front  of  the  equator 
about  a  quarter  of  an  inch— 6  to  7  mm.— from  the  cornea.  This  same 
description  applies  to  the  other  three  recti  muscles. 


QUIZ  ON  LESSON  THREE. 

1.  How  many  nnisclcs  control  the   action  of  the   eyeball? 

Name  them. 

2.  What  does  the  term  "extrinsic  muscles"  mean? 

3.  Name  the  muscle  that  lifts  the  upper  lid. 

4.  Give  tlie  orijiin  and  insertion  of  the  two  ol)li(iue  muscles. 

5.  Give  origin  and  insertion  of  the  recti  muscles. 

6.  AVhich  side  of  the  base  of  the  orbit  is  the  trochlea  on? 

7.  Where  do  we  find  llie  iiilriiisic  muscles.'     Name  them. 

8.  Name    tiu'   nerves   llial    sui)ply   the    luolor   i)o\V('r   of   the 

extrinsic  iiinscles  and  whicli   one  of  lliein   also  sui)plies 
tlie  intrinsic  muscles .' 

9.  Study  the  two  ])la1('s  carcfnlly. 

10.     See  special  anatomy  on  nniscU^s  in  PART  TWO. 


Ketchum's  Lessons  ox  the  Eve  35 

LESSON  FOUR.     (Section  One.) 
THE  EYELIDS— (Palpebrae). 

Tlio  eyelids  arc  two  movable  curtains  placed  in  front  of  the 
eyeball  to  serve  as  a  general  protection  from  injury,  dust, 
excessive  light,  etc.  Along  the  margin  of  each  lid  are  hairs 
called  cilia  or  eyelashes.  There  are  two  or  more  rows  of  lashes 
in  each  lid,  being  longer  and  more  numerous  in  the  upper  lid 
and  curved  somewhat  upward,  while  those  in  the  lower  lid 
turn  in  the  opposite  direction,  downward.  These  lashes  should 
never  be  cut  or  trimmed  as  they  serve  to  prevent  small  parti- 
cles from  getting  in  between  the  lids. 

Each  lid  has  the  following  arrangement  of  parts  from  the 
skin  inward : 

(1)  Skin. 

(2)  Areolar  tissue. 

(.3)  Orbicularis  palpebrarum  muscle. 

(4)  Tarsal  plate. 

(5)  Palpebral  ligaments. 

(6)  Meibomian  glands. 

(7)  Conjunctiva. 

Palpebral  fissure  is  the  name  given  to  the  space  between 
the  edges  of  the  open  lids — (fissure  means  an  elongated  open-- 
ing). 

Conjunctival  sac  is  the  name  given  to  the  space  that  lies 
between  the  inside  of  the  eyelids  and  the  eyeball  because  of 
the  membrane  of  that  name  (conjunctiva)  which  lines  the  lids 
and  also  covers  the  front  part  of  the  sclerotic.  It  is  in  this 
sac  that  small  particles  are  held  that  get  "into  the  eye". 

Outer  canthus  is  the  name  given  where  the  edges  of  the 
upper  and  lower  lids  come  together  on  the  temporal  side. 

Inner  canthus  is  where  the  lids  join  on  the  nasal  side. 

Canthi  is  plural  of  the  word  canthus. 

Looking  at  the  lids,  closely,  yon  will  find  at  the  inner  can- 
thus  a  little  elevation  or  point  on  either  lid  where  there  is  a 
small  hole  (see  picture  in  Lesson  Five).     It  is  called  the 


36  Ki:TciirM's  Lessoxs  ox  thk  \\\e 

Puncta  larchrymalis. 

This  opening  in  each  lid  lends  to  a  canal  through  which  the 
oi'dinary  supply  of  lachrymal  fluid  called  tears,  is  drained  off 

into  the  nose.     There,  also,  at  the  inner  eanthns  Avill  l)e  found 

a  small  llesliy  spot  willi  a  \'r\v  line  hairs  in  it.     Tliis  is  called  the 

Caruncle. 

Close  to  the  inner  canthus  and  practically  attached  to  the 
eyeball  is  a  small  fold  of  loose  pink  tissue  which  is  called  the 

Plica  Semi-lunaris. 

(Plica  uu'ans  fold;  semi-luiuiris  means  half  moon).  It  is 
also  called  the  half  moon  fold.  This  niemhrane  is  the  vestige 
of  Avhat  in  the  early  career  of  man  was  his  third  eyelid.  It  is 
still  fouiul  fully  developed  in  birds  and  some  of  the  lower 
animals. 

The  different  parts  of  the  lids  besides  the  shin  may  bi-ietiy 
be  described  as  follows: 

Areolar  tissue  means  a  tissue  composed  of  white  and  yel- 
lowish til)res  widely  diffused  throughout  the  body.  Its  func- 
tion is  to  give  strength  and  elasticity  to  a  part  as  well  as 
serve  as  a  protection  from  injury.  In  the  lids  it  lies  next  to 
the  skin  and  acts  as  a  sort  of  a  cushion  to  protect  the  eyeball. 

Orbiculus  palpebrarum  muscle  is  described  in  Section  Two 
of  this   Lesson. 

The  Tarsal  plate  (tarsal  cai-tilage)  is  a  thin,  eartilagimnis 
tissue,  which  gives  form  to  the  lids,  and,  when  l)o1ii  lids  are 
closed,  forms  a  shield  Tor  the  eyeball  in  I'loiit.  Thr  eartilage 
of  the  upper  lid  is  miieh  largei'  than  th.-il  of  Hie  lower,  and 
at  its  upper  margin  is  allaehed  lo  the  mid  of  ihe  muselc  thai 
lifts  that  lid,  the  levator  palpebrarum. 

The  Meibomian  glands  aiv  small  sebaceous  tfallN)  glands 
imbedib'd  in  the  subslniiee  of  ihe  1ars;il  earlilages  and  are 
|)bice(l  sidi'  1»\  side  \-erlieally  in  each  lid  t'nmi  one  ciinllnis  lo 
the  other.  t'Ik'n-  number  aboul  thirl\-  in  Ihe  upper  lid  and  a 
few  less,  siiy  idimit  1  w cnly-lixt',  in  ihe  lowei'.  These  <_d;iiuls 
havi'  openings  on  Ihe  boi'der  n\'  ihe  lids  ah»ng  among  ihe  e\e- 
j.-ishes.  They  seefele  ;in  oil\  subslauee:  which  servi-s  to  lubri- 
cate IJH'  con  iuncli\  al  sae. 


Conjuncti' 


Meibomian  gland  in  tarsal 
plate 


n 

->{\^  (J  ^^ Tendon  of  levator  palpebrse 

f^^T!v~;^5?  snperioris 

Skin 


Orbicularis  palpebrarum 


Ejelashes 


Showing  the  Structure  of  the  Upper  Lid. 


Ketciium's  Lessons  on  the  Eve  37 

The  Conjunctiva  is  a  thin  mucous  mcinbrano  which  Ijcgins 
at  the  edges  of  the  lids,  lines  them  and  folds  back  upon  the 
sclera  (to  which  it  is  loosely  attached)  and  covers  the  front  of 
the  eye  to  the  margin  of  the  cornea.  The  part  lining  the  lids 
is  called  the  palpebral  conjunctiva;  where  it  folds  back  upon 
the  eyel)nll  it  is  caHed  tlic  fornix  (arch)  ;  and  that  part  which 
covers  the  sclera  in  front  is  the  ocular  conjunctiva. 


38 


Ki:t(.' hum's  Lessons  on  the  Eye 


LESSON  FOUR.      (Section  Two.) 

THE  MUSCLES  OF  THE  EYELIDS  AND  EYEBROWS. 

Occipito-froiitalis  1 

Oi'biciilaris  i)alpel)rainiiii    I  j^n  supplied  by  the  seventh  nerve, 


Tensor-tarsi  j' 

Tendo  oculi  i 

Corriig'ator  sui)ereilii  ^ 


ilso  called  facial  nerve. 


Levator  ])alp('1)ra  su])('iio]'is  (in  part).     Tliii'd  nerve. 

The  occipito-frontalis  is  the  forehead  muscle.     It  elevates 
tlie  (\yehro\vs  and  ])i()dnees  Avrinkliiig  of  the  forehead. 


/'iffc , 
i  Ik 


^ 


E.  p.  L. 


Orbiculari.s  palpebrarum. — The  palpebral  and  orbital  portions  are 
easily  recognixed,  though  the  line  of  separation  is  not  always  to  be 
seen.  ('.  S.  i)oiiits  to  the  corrugator  supercilii:  h.  V.  L..  iiit«M-nal  i^al- 
I)ebral  llKanient :  !•:.  I'.  1...  iiosition  of  external  palprhral  li.uanient. 
(After  Henle.) 


Ketciium's  Lessons  on  the  Eve  39 

The  orbicularis  palpebrarum,  (sphincter  oculi)  is  the  chief 
muscle  of  the  lids  and  is  a  powei'fnl  volunt;ii\v  spliincter,  con- 
sisting of  an  orbital,  palpebral  and  lachrymal  portion.  It  is 
a  thin.  Hat  muscle  which  lies  immediately  under  the  skin,  en- 
circling the  eye  and  has  fibres  ])rjinching  out  connecting  it 
with  the  brow,  forehead  and  cheek.  By  its  action  the  lids  may 
be  j)artially  or  gently  closed  or  they  nmy  be  tightly  squeezed 
together. 

The  tensor-tarsi  or  Horner's  muscle  is  a  thin  muscular  sheet 
situated  at  the  inner  angle  of  the  orbit  behind  the  lachrymal 
sac.  This  muscle  is  really  a  deep  portion  of  the  orbicularis 
palpebrarum.  Tt  divides  the  two  portions  Avhich  cover  the 
posterior  ])art  of  each  canaliculus.  \n  front  of  the  lachrymal 
sac  is  the  tendo  oculi,  a  short  tendon  about  G  mm.  long  and 
can  be  felt  as  a  little  ridge  by  pressing  the  finger  against  the 
side  of  the  nose  at  the  inner  canthus.  The  tensor-tarsi  and  the 
tendo  oculi  both  serve  to  empty  the  lachrymal  sac  by  involun- 
tary compression,  thereby  forcing  its  contents  down  through 
the  nasal  duct  and  from  there  into  the  nose. 

The  corrugator  supercilii  is  a  short  ribbon-shaped  muscle 
located  at  the  upper  ridge  of  the  frontal  bone  at  about  the 
middle  of  the  eyebrow.  Its  action  is  to  draw  the  middle  of 
the  eyebrow  inwards  and  downwards  which  gives  the  froAVJi- 
ing  aspect  to  the  face. 

The  levator  palpebra  superioris  acts  in  opposition  to  the 
orbicularis  and  elevates  the  uppei'  lid.  It  has  been  mentioned 
in  connection  with  the  intra  orbital  muscles  as  it  lies  entirely 
within  the  orbit. 


40  Ki:iciiim's  Lf.ssoxs  on  tiik  Eve 


QUIZ  ON  LESSON  FOUR. 

1.  AVlial  is  tlic  niiatoinical  name  foi'  eyelid? 

2.  Locate  tlie  ])ali)el)fal  fissure.     State  wliat  it  reefers  to. 

3.  AVhat  is  meant  by  outer  eantlius  and  iuiu'r  eaiitluis.' 

4.  State  just  exactly  Avluit  constitutes  tlie  conjunctival   sac. 

5.  Make    a   diagram    showing    in    tlie    ])ro])ci'    ])osition,    the 

puncta,  caruncle  and  the  half  nu)on  fold. 

G.  "What  does  the  plica  semilunaris  represent.' 

7.  AVhich  A\ay  do  the  (\velashes  turn  in  each  lid? 

8.  Name  the  layers  of  the  lid  fi'om  tlie  skin  inward. 

9.  AVliich  layer  gives  form  to  the  lids? 

10.  TTow     many   meibomian    glands    in    each    lid    and  what  is 

their  function  ?    "What  sei)a rates  them  from  the  eyeball  ? 

11.  Describe  the  conjunctiva  ;  the  fornix. 

12.  Locate   the   iial|)ebral   conjunctiva;  ocular  conjunctiva. 

13.  Name  lln^  ])i-incipal  muscles  of  llie  lids  and  eyebrows. 

14.  Where   do    A\'e    lind    the    orbicularis   ])ali)ebrai'um  ?      What 

nerve  coni  racis  it  ? 

1.").      Just  wliere  is  tlie  1  ensoi'-tai'si  and   tendo  oenli   relatix'e  to 
the   lachrymal   sac'      Whal    aic  they    for.' 

If).     Where  is  the  corinigator  supercilii  and  what  is  its  action.' 


Ketch um's  Lessons  ox  the  Eve  41 


LESSON  FIVE. 

THE  LACHRYMAL  (Lacrimal)  APPARATUS. 

This  refers  to  the  secretion  of  "tears"  and  of  their  disposal, 
and  is  divided  into  a 
Secretory  portion  and  an 

Excretory  portion.  The  former  consists  principally  of  the 
lachrymal  oland ;  but  as  a  matter  of  fact,  the  moisture  that 
commonly  cleanses  the  ocular  and  conjunctival  surface  comes 
from  the  mucous  follicles  of  the  palpebral  conjunctiva,  while 
more  copious  supplies  of  tears  are  furnished  by  the  lacliryiual 
gland.  Patients  often  complain  of  dryness  of  the  eye,  the  lid 
seems  to  stick  to  the  ball.  This  is  the  result  of  the  conjunc- 
tiva being  affected  so  that  the  normal  secretion  is  somewhat 
lessened.  There  are 
two  lobes  to  the  gland;  an 

upper  lobe  oval  in  shape,  about  20  to  25  mm.  in  length  and 
12  to  14  mm.  in  thickness.  (See  cut  showing  apparatus  of 
right  eye).     The 

lower  lobe  is  smaller  and  is  sometimes  called  the 
accessory  gland.     The  gland  is  located  at  the  base  of  the  orbit 
at  about  the 

superior  external  angle,  lodged  in  a  depression  of  the  frontal 
bone  to  Avhich  it  is  attached  by  loose  connective  tissue;  the 
under  surface  rests  upon  the  eyeball  at  the 
fornix    (or  fold  of  the  conjunctiva  where  it  turns  from  the 
upper  lid  back  upon  the  eyeball). 

A  study  of  the  pictue  Avill  show  the  general  plan  of  the 
entire  apparatus.  From  the  gland  Avill  be  seen  several  little 
tubes — about  ten — Avhich  connect  the  gland  with  the  surface 
of  the  eyeball  through  the  thin  tissue  between  them  and  it  is 
through  these 

Lachrymal  ducts  that  the  slightly  alkaline  fluid— the  tears- 
is  sprayed  onto  the  globe. 


42  Kktciu'm's  Lessons  ox  the  Eve 

Tlio  Excretory  Part  is  located  at  the 
inner  canthus  and  consists  of  the  parts  that  diain  the  tears  off 
into  the  nose.    These  parts  are  the 
Puncta  lachrymalis   (hichi'vninl  ])oint)  ; 
Canaliculus  (canal)  ])hiral,  canaliculi; 
Lachrymal  sac ; 
Nasal  duct. 

The  puncta  lachrymalis  is  a  very  small  oix'iiiiiii'  on  tlie  edge 
of  the  lid  connecting  with  the 

canal  about  7  or  8  mm.  in  lengtli  whicli  are  directed  toward 
the  nose  where  the  upper  canal  and  tlio  lowrr  one  meet  and 
form  a  common  canal  that  connects  Avitli  the  laclirynial  sac. 
From  here  the  drainage  is  downward  through  a  connecting 
tul)e,  the 

nasal  duct  Avliich  is  directly  continuous  witli  the  sac  and  leads 
into  the  nose. 

The  tears  are  drawn  into  the  sac  from  the  inner  canthus 
where  they  settle  in  a  little  depression,  th(^ 
Lacus  lachrymalis,   by  suction,  the  motor  power  ])eing  sup- 
ported l)y  tlie 
tensor-tarsi  or 

Horner's  muscle,  wliich  consists  of  two  ])ai-1s  of  about  \2  iiiin. 
long  arranged  so  as  to  compress  each  caiiab  wliieli  they  do 
involuntarily,  and  very  often,  thus  sucking  tlie  secretion 
through  the  puncta.  In  excessive  secretion  of  tears,  as  in 
crying,  there  is,  of  course,  an  overflow  u])on  the  cheeks.  Tliis 
is  called 
lachrymation. 


Ketchum's  Lessons  on  the  Eve 


43 


P..S 

11 

O  g 

2-1 

S!>. 

%  >> 

d  <n 

51 

si 

M 

44  Ki:tciiu.m's  Lessons  ox  the  Eye 

The  picture  illustrates  the  meibomian  jiiands  as  well  as  the 
lachrymal  apparatus.  Near  the  lachrymal  gland  will  be  seen 
»)  or  7  little  spots  which  ai'e  to  show  where  and  how  the 
tears  i>t't  from  the  gland  through  the  conjunctiva  onto  the 
eyeball.  Just  h(Me  the  picture  is  somewhat  misleading,  as 
the  conjunctiva  is  made  to  appear  to  be  on  the  outside,  or 
external  to  the  meibomian  glands  instead  of  inside  next  to  the 
eyeball. 

The  little  dots  along  the  edges  of  the  lids  are  to  represent 
the  ordinarily  invisible  opening — meibomian  follicles — at  the 
ends  of  the  meibomian  glands  through  which  an  impercepti- 
ble oily  secretion  passes  to  lubricate  the  conjunctival  sac,  thus 
permitting  the  eve  to  move  about  without  friction  with  the 
lids. 


QUIZ  ON  LESSON  FIVE. 

1.  AVhat  is  meant  by  the  term  "lachrymal  apparatus"?  Give 

its  divisions. 

2.  AVhy  do  people  complain  of  dryness  of  the  eye? 

3.  Describe  the  jjosition  of  the  tAvo  lobes  of  the  laehi'ymal 

gland. 

4.  How  and  through  what  medium  does  the  secretion  from 

the  gland  get  onto  the  eyeball? 

5.  Diagram  and  name  each  part  of  the  excretory  apparatus. 

6.  How  is  drainage  affected?     (See  Tensor  Tarsi  and  Tendo 

Oculi,  lesson  4). 

7.  Do  the  meibomian    glands   ])c:w  nii\'   rrlntionship   lo   1lic 

lachrymal   a])i)aratus .'      If  so,  how.'      If   not.  wli\'  not.' 
S.     Where  do  mc   fiml  1lie  laeus  laclir\ mails .' 
0.     What  is  tJH'  ])lnral  for  eanalicnlus  .' 
10.     Define  laelirymation. 

Note  to  the  Student. — You  have  now  learned  a  greal  deal 
about  the  ey(>  just  fi'om  Ibese  few  lessons.  Xow  lake  anxone 
of  the  ]netures  and  1all<  lo  it  ;ind  llieti  show  it  to  sonuMtne  else, 
telling  liim  what  eaeii  !)art  is  and  what  it  is  for  and  how  it 
coniH'ets  u))  with  some  other  ])ait.  ele. 


Ketchum's  Lessons  on  the  Eve  45 


PART  TWO. 

Part  One  covers  the  anatomy  of  the  orbit,  the 
eye,  and  its  appendages  in  a  general  way  so  that 
the  student  can  get  a  fairly  complete  conception 
as  a  whole  of  Avhat  is  expected  of  him  to  master. 
However,  there  are  some  essentials  that  he  should 
know,  as  well,  that  are  not  found  in  any  text  on 
the  eye,  and  would  require  some  research  to  cover. 
These  will  he  found  fairly  well  presented  in  Part 
Two. 


46  Ki:tciil'm's  Lessons  ox  tjik  Eve 


PART  TWO. 

GROSS    DESCRIPTIVE    ANATOMY    AND    PHYSIOLOGY 
OF  THE  EYE. 

THE  SCLEROTIC. 

This  is  sometimes  called  the  Sclera  or  the  white  of  the  eye 
and  is  an  opaque  fibrous  membrane  covering  five-sixths  of 
the  entire  eyeball.  In  old  age  it  sometimes  becomes  a  dnll 
yellowish  hue,  due  to  infiltration  of  fat,  especially  near  the 
margin  of  the  cornea.  Its  greatest  thickness  is  found  at  the 
back  part  around  the  optic  nerve  where  it  is  about  one  mm. 
From  this  region  forward  it  grows  thinner  until  it  is  from 
four-tenths  to  six-tenths  of  a  unn.  only.  AVhere  the  sclera 
and  cnniea  come  together  is  called  the 
sclero-corneal  margin. 

It  is  scantily  supplied  with  blood-vessels  and  consequently 
gets  its  nourishment  from  its  own  lymphatic  canals  with 
■which  it  is  abundantly  supplied.  Its  nerves  are  derived  from 
the  ciliary  nerves. 


THE  CORNEA. 

The  cornea  is  legaidcd  as  the  fi'oiit  window  lo  tlu'  eye 
and  as  an  object  glass  of  the  ocular  camera  it  is  one  of  the 
most  important  portions  of  the  apparatus.  Being  necessarily 
placed  at  the  front,  and  exposed  whenever  llic  eyelids  are 
parted,  it  is  more  frequently  injured  than  any  oilier  pail  of 
the  eye.  It  comprises  one-sixth  of  tlie  external  lunie  or  eoat 
of  the  eye  and  its  essential  features  are  as  folknvs: 

It  lias  five  layers: 

( 1 )  Epithelium. 

(2)  Bowman's  membrane,  or   Anterior  elastie   lamina. 

(3)  True  corneal  tissue  (Cornea  Propria)  which  is  the 
center  la\-er  ami   iiiueh   thicker  than   aii>    ol'  the  others. 

(4)  Descemets  membrane  or  Postei-ior  elastic  lamina. 

(5)  Endothelium. 


Ketchu-m's  Lessons  on  the  Eve  47 

Diameter — Vertical  11  mm.;  horizontal  12  mm. 

Refractive  power — al)out  42  dioptres. 

Radius  of  curvature — 7.8  mm.  horizontal  meridian  and  7.7 
in  the  vertical. 

Index  of  refraction — ^1.33. 

Blood  vessels — none. 

Nerves— highly  sensitive— 60  to  80  branches  of  the  anterior 
ciliary  nerves  enter  the  cornea. 

The  cornea  attains  its  permanent  dimensions  very  early  in 
life  and  varies  but  little  after  the  third  year.  It  developes 
faster  than  the  rest  of  the  eye. 

Nutrition — As  the  cornea  has  no  blood  vessels  from  which  to 
get  nutrition  and  grossly  speaking  is  a  network  of  cells,  it 
maintains  itself  upon  the  vital  force  of  these  cells,  causing 
an  inter  cellular  flow  of  lymph  Avhich  remains  al)out  equal 
during  life. 

Some  interesting  experiments  have  been  made  to  deter- 
mine the  behavior  of  the  cornea  with  regard  to  the  rays  of 
the  invisible  portions  of  the  spectrum.  Its  power  of  absorp- 
tion of  the  infra-red  or  heat  rays  is  a  little  superior  to  that 
of  water,  but  not  notably  so.  The  chemical  or  ultra-violet 
rays  also  appear  to  pass  through  the  cornea  without  sensible 
diminution. 


ARCUS  SENILIS. 


In  elderly  persons  there  is  often  seen  a  narrow  gray  crcs- 
entric  line  either  around  the  cornea  or  at  its  upper  border. 
This  is  called  arcus  senilis,  or  the  arch  of  old  age.  It  never 
interferes  with  the  vision,  although  it  may  extend  some  dis- 
tance toward  the  center.  It  is  occasionally  seen  in  young 
people,  but  is  usually  not  seen  before  fifty  or  sixty  years  of 
age,  owing  to  decrease  in  nutrition  with  advancing  years. 


48  Ki:t(  II  i.m's  Lessons  ox  the  Eyi-: 

THE  IRIS. 

The  iris  is  ;i  colored  iiieni])i-aiie,  circular  in  fonii,  liaii^iuii 
beliind  tlie  cofiiea  directly  in  front  of  tlie  lens  and  in  contact 
■\vitli  i1  and  ])erfofated  at  about  its  center  by  an  a])erliire 
of  varial)b'  size  called  the  pupil. 

In  iiew-boi'ii  Avinte  children  the  iris  is  almost  always  blue. 
This  is  due  to  the  fact  that  its  piguicnt-cells  do  iu)t  develop 
until  sometime  after  birth,  the  coloration  not  being  complete 
until  after  the  second  year.  In  Albinos  the  i)ignient  is  en- 
tirely absent.  The  distribution  of  i^ignient  varies  great  1\'  in 
different  individuals. 

Diameter — K)  to  12  mm. 

Thickness — A  mm. 

Diameter  of  pupil  ranges  from  3  to  (3  mm. 

Blood  supply — The  blood  vessels  of  the  iris  come  from  the 
two  branches  of  the  Ophthalmic  artery,  known  as  tlie  long 
posterior  ciliai'y  ai-teries,  also  the  antcn-ior  ciliary  arteries. 

Nerve  supply — The  contraction  of  the  ])n])il  occurs  by  the 
action  of  a  branch  of  the  third  nei've  uj)on  a  narrow  mus- 
cular band,  called  the 

Sphincter  pupillae  which  encircles  its  border;  and  dilation 
occurs  1)\-  relaxation  of  the  sphincter  and  contraction  of  the 
7'adiating    niuscidar   fibres   called    the 

Dilator  pupillae,  which  action  is  coid  rolled  by  the  symjm- 
thetic  nei'N'e. 

The  structure  of  the  iris  ])rcsents  two  chief  layeis — the 
iridial  stroma  or  body  ])i'o|)ei'  and  the  piiiuicnt  la\cr:  these 
include   live   subdaycrs   - 

1.  Anterior    endot  lu'linm. 

2.  Anterior   boiuidary   layei'. 
.'■?.      A'ascular   stroma    layer. 

4.      I'ostei'ior    limiting    la\-er. 

.").      I'i-mcnt    layer. 

'I'he  vaseidar  stroma  la\cr.  rormin-  the  bnik  of  the  ii'is. 
consists  of  loose  connectixe  tissne  support  inii  the  nnnu'i-ous 
blood    vessels  and    nei'Ncs    which    occu|)y    this    la\ei'. 


This  picture  is  not  of  the  eye  itself,  but  is  a  diagram  made  to  show 
why  the  second  coat  is  called  the  vascular  coat.  The  word  vascular 
means  tube  or  tubes.  Blood  vessels  and  nerves  are  tubes.  The  general 
color  of  the  choroid  is  brown,  not  blue.  However,  it  is  customary  in 
coloring  anatomical  pictures  to  show  the  arteries  red  because  the  blood 
within  them  is  bright  red,  while  in  the  veins  it  is  a  much  darker  red, 
and  as  seen  through  the  skin  presents  a  bluish  tinge.  For  general 
blood  supply  see  "Ophthalmic  Artery". 


Ki-:TciirM's  Lkssoxs  ox  Tin-:  Evi-:  49 


THE  CILIARY  BODY. 

The  ciliary  body  is  that  portion  of  the  second  tunic  direct- 
ly back  of  the  iris  and  extending  l)ack  to  the  choroid.  It 
consists  of  two  parts — ciliary  muscle  and  ciliary  processes, 
which  foi'iu  a  sort  of  a  ring  around  the  margin  of  tlie  h'ns. 
The  ciliary  muscle  being  close  to  the  sclera  iiear  the  sclero- 
corneal  junction,  while  the  processes  are  a  little  farther  back 
or  uiuler.  It  is  supplied  by  a  branch  of  the  thii'd  iierve  and 
possesses  the  involuntary  function  of  adjusting  the  convexity 
of  the  lens — called  accommodation.  The  ciliary  muscle  con- 
tracts and  pulls  the  ciliary  processes  forward  toward  the  lens, 
thus  relaxing  the  tension  on  the  suspensory  ligament  which 
holds  the  lens;  with  the  tension  relaxed  the  pressure  is  re- 
moved ott'  the  anterior  surface  of  the  lens  which  then  as- 
sumes a  more  convex  condition,  sufficient  to  keep  images  up- 
on the  retina  at  different  distances  at  which  the  eye  may  be 
directed. 

The  ciliary  processes  aie  some  seventy  or  eighty  slight  ir- 
regular folds  and  are  reallly  the  forward  continuation  of  the 
choroid  and  it  is  to  tht'se  that  the  suspensoi'y  liganu'nt  is 
attached.  They  are  the  most  vascular  portion  of  the  eye- 
ball, principally  composed  of  pigment  and  numerous  blood 
vessels  and  this  body  is  the  principal  source  of  the  aqueous 
humor. 


50  Ki:tciii-m's  Lessons  ox  the  Eve 


study  this  diagram  carefully  as  it  represents  a  cross  section  of  an 
eye  cut  through  just  back  of  the  ciliary  body  and  shows  the  relation  of 
one  part  to  any  other  part  of  that  region  of  the  second  coat  as  indi- 
cated by  lines.  The  student  will  disregard  a.  b.  c.  and  d.  and  begin  at 
the  w^hite  spot  in  the  center,  the  pupil.  From  the  margin  of  the  pupil 
to  the  next  ring  is  the  iris.  From  this  ring — the  iris — the  ciliary  body 
begins  and  extends  backward  toward  the  choroid  about  6  mm.  Close 
to  the  iris  you  see  what  looks'  like  a  round  string  of  elongated  l)eads 
to  illustrate  the  ciliary  processes.  The  letter  g.  points  to  the  corona 
radiata,  which  means  the  iris  setsi  in  a  raised  ring,  and  it  is  in  this 
ring  that  the  lens  belongs.  In  the  study  of  the  lens  and  in  accommoda- 
tion this  picture  should  be  kei)t  in  mind. 


THE  CHOROID. 

The  choroid  is  a  dark  l)ro\vii  iiicinl)i-aiH'  lyini>-  l)c1\vecii  llir 
sclera  and  the  retina  and  const itulcs  the  posterior  two-lliirds 
of  this  second  coat  or  tnnic  fiom  the  ciliary  l)ody  hack'.  Il 
is  vei'y  tliiii.  varying  fi'oiu  .<)(i  of  a  inni.  in  fiont  lo  alxnit 
.1  of  a  111  111.  at  the  ])ack.  H  is  also  eallt'd  llic  vascular  coat 
because  it  consists  mainly  of  hlood  vessels  wliick  arc  nniled 
l)y  delicate  connective  1i,ssn(>  containinti  iiiiniei-ous  pi^ineiiteil 
cells.  The  arteries  are  llie  shoi-t  ciliary.  Its  ruiictioii  lliioui-h 
its  vessels  is  cldelly  1o  serve  iniliilion  to  thf  reliiia.  \i1reons 
and  lens.  It  forms  tlie  daik  coaliiiti-  t)!'  Ilic  iiiterior  of  Ihe 
e.vel)al]  ami  its  (hii-k  ])i^iiieii1  is  nature's  provision  to  modify 
the  intensity  of  liyht  that   enters  llirouiih  (he  pupil. 


Ketciium's  Lessons  on  the  Eve  51 


THE  RETINA. 


The  retina  is  a  very  thin  delicate  membvano  which  con- 
sists principally  of  an  expansion  of  the  optic  nerve.  It  is  the 
inner  coat  or  tunic  and  extends  forward  to  the  ciliary  body 
where  its  termination  is  called  the  ora  serrata.  From  there 
on,  devoid  of  nerve  fibres  and  much  thinner,  it  is  continued 
on  forAvard  over  the  inner  surface  of  the  ciliary  body  and 
posterior  surface  of  the  iris.  In  the  living  eye  it  is  trans- 
parent and  of  a  purple  red  color ;  after  death  it  soon  becomes 
opaque.  It  is  connected  with  the  choroid  at  the  entrance 
of  the  optic  nerve  at  the  back  and  at  the  ora  serrata  in  front, 
otherwise  it  simply  lies  upon  it,  but  is  not  attached  to  it.  On 
this  account  vision  is  often  destroyed  by  detachment  of  the 
retina  from  its  position  against  the  choroid. 

The  minute  anatomy  of  the  retina  is  very  complicated.  It 
is  the  complete  development  of  this  part  of  the  eye  that  is 
especially  necessary  to  good  vision.  Vibrations  of  light  reach 
it  from  "all  directions  in  front  of  the  eye,  but  its  region  of 
most  distinct  vision  is  about  1  mm.  to  the  temporal  side 
of  the  optic  axis.  This  is  called  the  macula  lutea  or  yellow 
spot  which  is  slightly  oval  and  approximately  2  mm.  in  its 
great  diameter  which  is  horizontal.  Near  the  center  of  the 
yelloAv  spot  occurs  a  small  depression  knoAvn  as  fovea  cen- 
tralis or  center  of  focus.  From  the  fovea  to  the  center  of  the 
optic  disc  it  is  about  4  mm.,  the  optic  disc  being  about  1.5  mm. 
in  diameter. 

The  retina  has  ten  layers  in  the  order  named  from  the 
choroid  inward. 

1.  Pigmentary  layer.  6.     Internal  nuclear  layer. 

2.  Layer  of  rods  and  cones.    7.     Internal  gi'anular  layer. 

3.  External  limiting  mem-       8.     Vascular  layer. 

brane. 

0.     I  ibrous  layer. 

4.  External  nuclear  layer.  ,   ,.     .  . 

10.     Internal  hmitnig  mem- 

5.  External  granular  layer.  brane. 


52  Kiyiciii'M's  LiissoNS  ox  the  Eye 

The  second  layer  is  of  tlic  most  interest  because  ui)oii  its 
pi'o])t'r  ik'veloj)iiiciit  depends  the  best  visual  acuity.  At  hiitli 
+here  are  :i,;^(i(),0()()  cones  and  about  180,000,000  rods  in  lliis 
layer  and  it  is  upon  the  furtlier  development  of  tlu'  eye  that 
j>()od  vision  depends.  Should  anything  interfere  with  the  com- 
plete groAvth  of  the  retina  to  prevent  development  of  the  num- 
ber of  cones  to  the  extent  of  about  7,000,000  the  vision  is  never 
perfect  and  cannot  be  made  so  with  glasses.  In  the  distribu- 
tion of  these  cones  it  has  been  found  by  microscopical  exam- 
ination that  from  the  ora  serrata  back  toward  the  macula  they 
gi-adually  1)ecome  more  numerous  and  closer  together  until 
within  the  nuicuhi  there  are  about  13,000  cones  and  no  rods 
at  all. 

The  rods  and  cones  are  the  terminal  organs  of  the  optic 
nerve;  receive  vibrations  of  light  which  fall  upon  the  retina 
and  connect  these  virbrations  into  impulses  which  are  carried 
by  the  different  l)ranches  of  the  optic  nerves  and  tracts  to  the 
brain ;  here  they  pi'oduce  the  sensation  of  light.  When  an 
image  falls  npon  any  otlier  part  of  the  retina  tliere  is  indis- 
tinct vision. 


Ki'yrciirM's  Licssoxs  ox 


Kvr. 


53 


A,  A  cone  and  two  rods 
from  the  human  retina 
(modified  from  Max 
Schultze) ;  B,  Outer 
part  of  rod  separated 
into  discs. 


Meinbraua  liiuitans  interna 

Diagramatic  Section  of  the  Human 
Retina  (modified  from  Schultze). 


Surface  view  of  retina,  showing  disposition  and  relative  number  of 
the  rods  and  cones.  (Kolliker.)  1,  from  the  fovea — only  cones:  2,  from 
the  margin  of  the  macula  lutea:  3,  from  midway  between  the  fovea  and 
the  ora  serrata;  a,  profile  of  larger  inner  segment;  b,  of  smaller  outer 
segment:    c,  rod. 


54  Kktchum's  Lessons  on  the  Eye 


THE  OPTIC  NERVE. 

T\\v  optic  nerve  is  iciiardcd  as  pai't  of  the  l)raiii,  and  is  de- 
visable into  tlut'c  portions,  cranial,  orbital  and  ocular  portions. 
It  is  about  50  mm.  long  fi'oni  the  eye  to  the  opiic  connuissure 
(also  called  the  optic  chiasm),  wbere  it  meets  the  optic  nerve 
coming  from  the  other  eye.  It  is  :U)  nun.  in  llic  oibit.  1(»  mm. 
in  the  optic  canal  at  the  apex  of  the  ori)il  and  1()  iniii.  intra- 
cranial (within  the  cranium  or  skull).  Behind  the  commissure 
the  two  optic  nerves  become  the  optic  tract.  The  nerve  is 
al)out  ,")  nnu.  across.  It  has  the  foi'ni  of  a  moditied  S  as  it 
lies  in  the  orbit,  thus  allowing  the  eyeball  to  move  about  with- 
out tension  on  the  nerve. 

OPTIC  DISC. 

Optic  Disc.  Optic  Nerve  entrance.  Optic  papilla.  Nerve 
head.  Blind  spot.  (Sometimes  improperly  called  Torus  Op- 
ticus.) This  is  the  termination  of  the  optic  nerve  as  it  pierces 
the  eyeball  and  spreads  out  to  form  the  inner  layer  of  the  retina 
—the  internal  limiting  mend.)rane.  Nornuilly,  the  optic  disc  is 
nearly  circular  in  outline  and  is  about  1.5  mm.  in  diameter.  It 
is  located  about  3.5  mm.  to  the  nasal  side  and  about  1  mm.  above 
1he  line  of  fovea  centralis.  The  optic  axis  of  the  eye  being  be- 
tween these  two  points.  It  has  a  ])inkish  tint  and  on  careful  ex- 
amination, is  seen  to  present  differently  colored  zones.  (1)  A 
central  clear  spot,  which  is  the  funnel-like  depression  from 
which  emerges  the  central  retinal  vessel.  (2)  A  vascular  zone 
containing  many  capillaries.  (3)  A  narrow  light  l)aiid.  which  is 
the  connective  tissue  ring.  (4)  Sui'rounding  all,  the  <lai'k  chor- 
oidal zone.  Its  size  as  seen  with  the  ophlhahnoscope,  direct 
method,  in  the  emmetropic  eye  is  said  to  be  lifteeii  times  larger 
than  actual.  In  the  hy|)er()i)ic  eye  it  is  comparatively  smaller 
and  in  myopia  greater.  Whoever  ligured  it  out  that  the  mag- 
nitication"  was  fifteen  times  must  have  ovci'h)oked  the  actual 
facts  in  the  case,  if  the  disc  is  1..')  mm.  in  size  and  we  midli- 
l)ly  that  with  15  we  get  a  diauu'ler  of  2'J.5  unii.  oi'  almost  an 
inch.  Never  x'el  have  I  seen  a  disc  look  anywhere  ueai'  that 
si/.i'.      .\t    most    it    appears  to   be  alio\i1    17   mm. 

PORUS  OPTICUS. 

I',, Ills  opticus  is  the  physiological  excavation  and  passage 
on  Ihc  nasal  side  of  tlic  optic  disc  wh.Mc  the  ivtiual  vess.'ls 
are  seen. 


Ketciium's  Lessons  on  the  Eye  55 


CAPSULE  OF   TENON 


(Note — See  "orbital  fat") 

Carefully  study  this,  as,  usually  given  in  text  books,  it  is 
somewhat  difficult  to  understand  just  what  the  capsule  really 
means.  Look  at  the  pictures  shown  here  as  you  read  this. 
The  Capsule  of  Tenon,  also  called  oculo-orbital  fascia,  in- 
sheathes  all  the  organs  Avhich  pass  through  it  and  forms  a 
cup  for  the  eyeball,  is  continuous  with  the  sheath  of  the  optic 
nerve  and  also  forms  a  secondary  attachment  for  the  ocular 
muscles.  It  is  a  delicate  opaque  membrane.  AVhile  it  appears 
as  a  part  of  the  eyeball,  it  is  not,  as  there  is  a  lymph  space 
between  it  and  the  sclerotic  which  it  covers  to  within  3  mm. 
of  the  sclero-corneal  margin  where  it  fuses  Avith  the  ocular 
conjunctiva  Avhich  covers  it.  It  is  taught  by  common  consent 
that  Tenon's  Capsule  is  a  socket  in  which  the  eyeball  rotates 
Avithout  change  of  position,  (meaning  the  socket  is  immovable 
and  the  ball  moves  about  in  it  AA^hen  the  extrinsic  muscles  pull 
in  it  in  any  direction).  Anatomy  shoAA's  that  this  is  out  of 
the  question  because  the  anterior  part  of  the  capsule  is  closely 
attached  to  the  sclera  in  front  of  the  insertion  of  the  recti 
muscles  close  to  the  cornea,  hence  the  two  move  tog-ether  upon 
the  cushion  of  fat  behind  them.  In  looking  at  the  picture  it 
Avill  be  seen  that  the  fibrous  tissue  of  the  sheaths  of  the  muscles 
is  continuous  Avith  that  of  the  socket,  the  effect  of  AA'hich  is 
partly  to  steady  the  eyeball  and  to  resist  the  backAvard  pull 
of  the  muscles.  It  Avill  be  understood  that  AA'hen  upon  operat- 
ing for  strabismus  a  muscle  is  cut  entirely  free  from  its  in- 
sertion, it  cannot  drop  out  of  position,  but  retains  its  rela- 
tionship Avith  the  other  extrinsic  muscles. 

The  Check  Ligaments  aid  in  this  also. 


56 


Ki/rciiiM's  Li:sso.\s  ox  tiik  Evi-: 


CHECK  LIGAMENTS 


The  check  ligaments  during  partial  contraction  of  the  external 
rectus  muscle,  the  internal  check  ligament  (1.  C.  L,. )  being  in  a  state  of 
maximum  relaxation,  and  the  external  (E.  C.  L.)  somewhat  stretched. 
(:Motais.) 

Diagram  intended  to  show  how,  during  full  contraction  of  the 
external  rectus,  the  external  check  ligament  (M  C.  L.)  is  stretched  to 
its  maximum  length,  and  the  internal  (I.  C.  J..)  is  slightly  stretched 
also.     (Motais.) 

Note. — It  will  be  observed  that  as  the  eye  is  sthown  turned  to  its 
utmost  there  is  no  pull  on  the  back  part  oif  the  ball  by  the  optic  nerve 
because  of  the  fact  that  the  nerve  is  very  flexible  and  of  a  modified 
S  sha])e,  which  admits  free  movement.  Most  pictures  showing  the  optic 
nerve  make  it  appear  to  be  practically  straight,  which  is  not  true. 


The  depth  of  the  orbit  is  4.')  mm.,  the  eye-ball  ii4  mm.,  sets  in  it 
leaving  3  or  4  mm.  at  the  base,  thus  from  the  back  of  the  ball  tO'  the 
optic  foramen  is  only  a  little  over  17  mm.,  and  as  there  is  :^.0  mm.  of  the 
Clitic  nerve  in  the  orbital  cavity  from  tlie  eye-liall  to  the  foramen,  that 
leaves  over  10  mm.  for  rotation. 


study  this  plate  carefully. 

It  shows  how  the  entire  eye-ball  and  the  muscles  as  well  as  the 
spaces  between  one  muscle  and  another  is  enveloped  in  the  same 
membrane.  At  the  ends  of  the  muscles,  where  cut,  it  will  be  seen  that 
each  one  is  completely  enveloped;  also  how  the  eye-ball  "sets  in"  the 
so-called  cup  and  that  a  little  to  the  anterior  of  the  middle  of  the  ball 
the  membrane  turns  back  on  the  inside  of  the  muscle  and  continues  to 
envelope  it  (them)  to  its  origin  at  the  apex  of  the  orbit.  The  lower 
left  Figure  presents  another  aspect  of  the  enveloping  membrane.  In 
the  lower  right  Figure  another  view  directly  from  behind  the  eye, 
forward,  emphasizes  the  fact  of  the  complete  enveloping  membrane 
called  The  Capsule  of  Tenon. 


Ketchum's  Lessons  on  ttte  K\k  57 


AQUEOUS  HUMOR. 

This  is  a  thin  clear  alkaline  fluid  occupying-  the  anterior  and 
posterior  chambers,  and  is  supplied  by  the  ciliary  processes. 
Its  index  of  refraction  is  1.33.  In  case  of  an  injury  or  opera- 
tion resulting  in  loss  of  aqueous  the  cavity  refills  in  a  few 
moments.  It  does  not  seem  hoAvever,  that  under  ordinary 
natural  conditions  a  very  i-apid  secretion  of  the  aqueous  takes 
place  because  its  principal  source  of  exit  is  through  the  spongy 
tissue  of  the  spaces  of  Fontana  at  the  sclera-corneal  margin 
where  it  is  drained  off  through  the  canal  of  Schlemm  by  the 
anterior  ciliary  veins.  To  a  lesser  extent  it  also  passes  out  by 
the  lymph-crypts  of  the  iris. 

The  extraordinary  solvent  properties  of  the  aqueous  humor 
makes  it  easily  affected  by  drugs  circulating  in  the  blood. 
Should  the  lens  substance  come  in  contact  Avith  it  in  small  por- 
tions at  a  time  it  completely  dissolves  it.  It  is  by  this  method 
that  soft  cataract  in  children  is  treated  and  the  lens  substance 
is  made  to  gradually  disappear. 


THE  VITREOUS  BODY  OR  HUMOR. 

is  a  soft  gelatinous,  perfectly  transpar-ent  substance  and  occu- 
pies the  posterior  cavity  called  the  vitreous  chamber  also 
hyaloid  cavity.  It  has  no  special  value  in  refraction  excepting 
its  index  of  refraction  which  is  1.33.  It  is  contained  in  a  very 
thin  transparent  capsule— the  hyaloid  membrane— which  sep- 
arates it  from  contact  with  the  retina.  It  gets  its  nutrition 
from  the  choroidal  vessels.  A  certain  amount  of  vitreous  may 
be  removed  without  seriously  injuring  vision,  and  it  seems  to 
be  rapidly  renewed  from  the  ciliary  processes  through  the 
zonula  ofzinn.  The  only  well  established  exit  of  fluids  from 
the  eye — the  aqueous  and  vitreous — is  that  at  the  angle  of  the 
anterior  chamber. 


Ketchum's  Lessoxs  ox  the  Eye 


THE  LENS  AND  ITS  CAPSULE. 


Before  birth  Avhile  gradual  development  of  Ihe  eye  is  taking 
place,  the  lens  is  supplied  with  its  nourishment  by  a  vascular 
membrane  which  surrounds  and  covers  it.  The  vascular  por- 
tion of  this  membrane  gradually  disappears  as  the  lens  com- 
pletes its  development  leaving  it  entirely  clear  and  it  there- 
after serves  as  a  capsule  or  complete  cover  for  the  lens  and 
])i'ot('Cts  it  from  the  surrounding  aqueous  humor. 

The  lens  is  hohl  in  position  by  the  suspensory  ligament,  also 
called  the  zone  of  zinn  and  zonula  of  zinn,  \\iiiel\  is  tlir  thick- 
ened portion  of  the  hyaloid  membrane  extending  from  the 
ciliary  body  to  the  margin  of  the  lens  on  its  anterior  surface. 

This  is  the  membrane  that  is  affected  by  the  ciliary  muscle 
when  "accommodation"  takes  place.  The  lens  is  a  biconvex 
circular  body,  lying  directly  behind  the  iris  and  in  contact 
with  it.  The  center  of  the  anterior  surface  of  the  lens  is  its 
anterior  pole,  and  is  about  2.3  mm.  from  the  back  of  the 
cornea  and  the  center  of  the  posterior  surface  is  its  posterior 
pole  which  is  about  15.6  mm.  from  the  retina.  It  is  a  little 
greater  in  convexity  behind  than  in  front.  The  central  ])or- 
tion  of  its  anterior  surface  is  opposite  the  pupil.  Its  posterior 
convex  surface  lies  against  the  hyaloid  membrane  iorming  a 
depression  called  the  patellar  fossa  or  hyaloid  fossa.  It  is  soft, 
elastic  and  transparent  and  is  alxtut  S.T)  nun.  in  its  tiansverse 
diameter  and  about  'SA  mm.  tliick  at  its  least  convexity  and 
4,  at  its  greatest. 


Radius  of  curvature.  (Anterior)     (PoslerioiO 

At   distant   vision,  h'ast  eurxature 10  mm.  (i  mm. 

At    cldsest  ^•isi()n    greatest    cuivatuie (•  mm.  5..")  nun. 

l^.'fraetive  ])o\vei'  about    1(1  D.     Index  of  refraetioii   1  }:!. 
Xuti-itioii  of  the   lens  is  su|)i)lie(l    fniiii   tiie  ciliaiy  body. 


Krc'i chum's  Lessons  on  the  Eve 


59 


ENLARGED  DIAGRAM  OF  THE  LENS 


No.  1. 


«;-a;^:: 


.%. 


- 

-r 

V 

>- 

s^'^ 

^ 

No.  2 


No.  3 


No.  1  shows  the  sectional  layers  of  the  lens  which  is  somewhat 
similar  to  that  of  an  onion,  and  opening  up  in  its  antero-posterior 
diameter. 


No.  2  shows  the  relative  iiroportions  and  curviture  of  both  surfaces 
of  the  lens  in  its  antero-posterioor  diameter  which  is  from  4  to  4.5  mm. 

No.  3  shows  the  greatest  diameter  of  the  lens  (al)out  S..5  mm.)  as 
it  is  held  in  position  directly  back  of  the  pupil. 

The  usual  diagrams  of  the  lens  seen  in  l)ooks  show  it  to  appear 
oblong  and  sharp  on  the  edge.  It  must  be  remembered  that  such  a 
picture  is  made  to  represent  the  eyeball — a  sphere — cut  in  half,  thus 
leaving  a  flat  side  view.  The  lens  cut  in  two,  vertically,  would  appear 
oblong  accordingly.  Its  edge  is  rounded— not  sharp— and  its  surfaces 
always  spherical,  as  shown  in  No.  2. 


60  Ki:T(rirM"s  Lkssoxs  on  ttte  Eyi; 


THE  CANALS  OF  THE  EYE 


Petit 's  Canal,  Hyaloid  Canal,  Schlemm's  Canal 

The  canal  of  Petit  is  a  narrow  channel  which  encircles  the 
niai'gin  of  the  lens.  It  is  filled  with  lymph  (a  fluid)  which 
conies  from  the  ciliary  \-essels  and  is  sn])])()sod  to  su])ply  nu- 
trition to  the  lens. 

The  hyaloid  canal,  also  called  the  canal  of  Stilling,  canal  of 
Cloquet  and  Central  canal,  is  a  very  fine  line  of  space  in  the 
vitreous  hunioi'  exteudino'  from  the  lens  hackward  to  the 
retina.  It  cannot  Ix^  seen  when  lookin«;'  into  the  interior  of 
the  vyo  Avith  the  o])hthalmoscope. 

The  canal  of  Schlemm  is  located  in  the  sclerotic  close  to  the 
margin  of  the  cornea  forming  a  sort  of  a  i-ing  arouml  the  front 
part  of  the  sclerotic.  It  is  really  a  channel  of  small  blood 
vess(ds  Avhich  serve  to  cari'y  oft"  the  debi'is  of  the  eye  l)ack  into 
the  circulation.  Directly  where  the  iris  aiul  the  cornea  come 
together  around  the  margin  are  a  numhei'  of  little  openings 
called  the  spaces  of  Fontana  through  which  the  Huid  passes 
from  the  anfei-ior  chaiid)er  in  order  to  get  into  the  canal  of 
Schlemm.  AVhenevei'  from  disease  or  injury  to  the  eye  this 
canal  is  closed,  the  drainage  of  the  eve  is  practically  destroyed 
and  the  pei'son  graduall\'  becomes  blind. 


Kktciium's  Lessons  ox  the  Evic  61 


ORBITAL  FAT. 

The  orbit  is  tilled  Avith  fat — adipose  tissue — Avhich  is  bound- 
ed in  front  by  the  capsule  of  Tenon  and  its  fibrous  expansions. 
It  is  very  delicate  in  structure  and  forms  an  almost  fluid  sup- 
port for  the  eye,  "well  adapted  for  its  movements  in  all  direc- 
tions without  pressure.  In  operating-  for  removal  of  the  en- 
tire eyeball  this  fat  is  not  disturbed,  as  the  cutting  is  first 
made  directly  around  the  margin  of  the  cornea  where  the  con- 
junctiva and  capsule  are  both  dissected  clear  from  the  scler- 
otic and  continued  on  to  the  insertion  of  the  recti  mnscles 
when  each  one  is  raised  with  a  hook  and  cut  close  to  the 
sclera.  The  blunt  pointed  curved  scissors  continue  to  follow 
close  to  the  sclera  separating  all  tissue  until  the  optic  nerve 
is  reached  and  cut,  when  the  entire  eyeball  is  then  removed 
from  the  pocket  or  inside  of  the  capsule.  The  muscles,  the 
fascia  and  the  fat  have  not  directly  been  disturbed  and  of 
course  retain  their  usual  relationship  and  together  form  a 
basis  for  the  use  in  Avearing  an  artificial  eye. 


CIRCLET  OF  ZINN— LIGAMENT  OF  ZINN— ZONE  OR 
ZONULA  OF  ZINN— TENDON  OF  ZINN 

The  circlet  of  zinn  is  the  vascular  circle  around  the  optic 
nerve  foi'ined  from  tAvigs  of  the  short  posterior  ciliary  arteries. 

The  ligament  of  zinn  is  the  loAver  part  of  the  common  tendon 
that  encircles  the  optic  foramen  at  the  origin  of  the  recti 
muscles  and  must  not  be  confounded  Avith  the  zone  of  zinn  or 
zonula  of  zinn,  Avhich  are  other  names  for  the  suspensory  liga- 
ment around  the  lens. 


LIGAMENTUM  PECTINATUM  IRIDIS. 

The  ligamentum  pectinatum  iridis  consists  of  a  mass  of 
spongy  tissue  and  occupies  the  angle  of  the  anterior  chamber 
Avhere  it  unites  the  iris  and  the  ciliary  muscle  at  the  inner 
corneal  bordin-.  It  is  intimately  connected  with  the  spaces  of 
Fontana. 


62  KRTcrir.M's  Li^ssoxs  ox  the  Eve 


BLOOD  SUPPLY. 


The  ophthalmic  artery  lias  been  mentioned  as  a  branch  of 
llii'  internal  carotid  artery.     These  two  pictiues  will  serve  to 
show  1lic   principal   blood  sii])])ly  of  the  bead.     It  is  called 
The  Carotid  System  of  Arteries. 

These  arteries  aie  found  on  either  side  of  the  neck  on  about 
a  vertical  line  with  the  ear.  There  is  a  main  stem  callecl  the 
Common  Carotid. 

At  a  i^oint  just  back  of  the  loAver  jaw  bone  it  separates  into 
t\\'o  branches  which  are  nanuHl 
The  External  Carotid  and 
The  Internal  Carotid. 

Each  of  these  a!t»ain  form  several  l)ranches  Avhicli  have  iianies 
according  to  the  local  parts  they  supply.  The  external  is  dis- 
tributed about  the  external  part  of  the  neck  and  head  while 
the  internal  is  contined  almo.st  entirely  to  the  contents  of  the 
cranial  cavity.  One  other  blood  sujjply  of  the  brain  comes 
from  the  Vertebral  arteries.  It  will  be  observed  in  the  picture 
that  the  ophthalmic  ailery  bi-anches  off  from  the  carotid  close 
to  the  a])ex  of  Ihe  orbit  just  back  of  the  optic  foramen  and 
from  there  )>asses  llii-ouiih  the  foramen  along  Avith  the  optic 
nerve  into  tiie  orbit  where  it  continues  forward  under  the 
lower  border  of  the  superior  obli(iue  and  its  i^ulley — trochlea — 
to  th(>  ])ase  of  the  orl)it  where  it  terminates  in  two  bi'anch(>s. 
Altogethei'  the  o])!)!  ha  I  ni  ic  ar1er\  ihe  Iruiik  loses  itself  into 
ten  separate  branches  and  thus  serves  1o  sujjplx'  iiuli\idual 
l)arts  of  the  conlenis  of  the  oibital  cavity. 


Showing  location  of  the  Cartoid  arteries  and  where  the   Internal 
l)ranches  off  and  passes  back  underneath  the  ear  and  up  into  the  skull. 


This  picture  is  to  show  the  connection  of  the  Ouhthalmic  artery 
rith  the  Internal  Cartoid  artery. 


SupTaorbilal  artery 

LACHRYMAL  GLAND 

Superior  rectus,  cut 

EYEBALl 


External  rectus 

Lachrymal  artery 

Superior  rectus,  cut 
Inferior  ophthalmic  lein 
Superior  ophthalmic  leiu 


OPTIC  XER  IX 

Common  ophthalmic  vein 


Commencement  of  superior 
ophthalmic  vein 

Reflected  tendon  of  superior 

oblique 
Ophthalmic  artery 


Anterior  ethmoidal  artery 

fjiij- —   Posterior  ethmoidal  artery 
Ciliary  arteries 
Levator  palpebrae,  cut 
Ligament  of  Zinn 
Ophthalmic  artery 

OPTIC  COMMISSURE 


Internal  carotid  artery 


Ketc hum's  Lessons  on  the  Eye  63 


THE   VEINS   OF    THE    ORBIT 

It  will  be  remembered  that  the  ophthalmic  artery  carries  the 
l)lood  into  the  orbit  from  the  brain  through  the  optic  foramen. 
(See  red  vessels  in  the  picture.)  At  the  base  of  the  orbit 
(in  front)  it  finds  its  way  into  the  veins  (see  blue  vessels  in 
cut)  which  gradually  enlarge  as  they  go  l)ack  towai'd  the  apex 
until  they  form  two  main  trunks— the  superior  ophthalmic  vein 
and  inferior  ophthalmic  vein  which  togethoi'  at  tlie  apex  form 
one  single  and  larger  vein — the  common  ophthalmic  vein  and 
from  here  passes  into  an  opening  called  the  cavernous  sinus. 

The  branches  of  these  veins  are 

(1)  The  superior  muscular  branches. 

(2)  The  ciliary  veins. 

(3)  The  anterior  and  posterior  ethmoidal  veins. 

(4)  The  lachrymal  vein. 

(5)  The  central  vein  of  the  retina. 


64 


Ki-rrciirM's  Li:.s.^o.\s  o.x  nij-:  Eve 


THE  EXTRINSIC  MUSCLES. 


liesides  the  oi'diiiary  text  on  tlieso  muscles  there  are  sevei'al 
points  that  a  rei'ractionist  should  know.  For  extended  read- 
inp:  involving-  every  progressive  thought  of  today  on  the  action 
of  these  muscles  the  reader  is  referred  to  the  two  large  volumes 
on  "The  ]\[uscles  of  the  Eye"  by  Lucien  B.  Howe,  ]\r.  1).,  of 
Buffalo;  also  a  single  volume,  "IMotor  Apjiai'atus  of  the  lOyo." 
by  George  T.  Stevens,  M.  D.,  of  New  Yoik.  Other  h.x.ks  of 
minor  value  are  of  course  on  the  mai-ket. 

Not  usually  mentioned  in  connection  A\ith  tin-  extrinsic 
muscles  there  are  check  lig-aments  (ligamentous  aileious — or- 
bital tendons)  that  should  receive  attention. 

These  names  are  given  to  small  fibrous  bands  that  connect 
each  extrinsic  muscle  close  to  its  insertion  on  the  globe,  to  sur- 
rounding parts.  The,v  serve  to  modify  any  extienu'  action  of 
the  muscle  j)roper,  acting  as  bands  of  restraint  as  wh'II  as  aid 
in  harmonious  action  of  two  or  more  of  the  muscles  and  are 
an  aid  to  i)erfect  binocular  fixation.  See  '•  Capsule  of  Tenon." 
Ill  regard  to  the  exact  distance  from  the  sclero-corneal  margin 
the  four  recti  muscles  have  their  respective  insertions,  there  is 
some  little  differoice  of  measurements  given  b\-  the  authors 
because  nature  varies,  but  a  fair  average  in  detail  is  as  t'ollows: 


Length 

Width  at 

Insertion 

on    Schlera 

Distance 

from 

Cornea 

Relative 
Power 

41     mm. 
40.6  mm. 
40     mm. 
41.8  mm. 

10.75  mm. 
10.75  mm. 
13       mm. 
la       mm. 

G   mm. 
7   mm. 

7  mm. 

8  mm. 

Stroiijiest 
'2d   stiongost 
'Ad   stroujifOSt 

Hxtcnial     Kt'dtus 

Superior  Rectus 

Weakest 

^'<.nr  allenlion  is  now  drawn  lo  tlie  WIDTH  of  ihe  insertion 
of  the  muscles  or  rather  the  tendinons  poiMion,  in  front,  of 
each  recti  muscle  of  from  10  to  IM  mm.  Xow  added  together 
the  total  distance  around  the  e\.'-l)all  co\cr<'d  l)\  the  inseilion 
of  these  fom-  muscles  is  ahout  Iti  mm.  As  the  eye!. all  at 
its  e(|uat()i'  is  alioul  2M  mm.  that  gi\cs  its  gi'eatest  cireum- 
eference  say  70  mm.  The  a ntero-post eri(U'  diameter  i)eing 
ahout  24  mm.,  we  now   TukI  that   the  insertion  of  these  muscles 


Ketc hum's  Lessons  on  the  Eve  65 

being  in  front  of  the  equator  are  at  a  point  Avhere  the  ciicuni- 
ference  is  somewhat  loss — say  62  mm.  This  knids  you  to  the 
fact  that  the  combined  length  of  these  insertions  practically 
make  a  complete  band  around  the  eye  leaving  only  about 
•4  nnn.  between  the  margin  of  each  insertion.  From  the  in- 
sertion backward  these  muscles  diminish  in  width,  swell  again 
at  the  center  and  become  smaller  again  at  their  origin  at  the 
apex  of  the  orbit. 

The  reason  we  do  not  see  these  nuiscles  at  their  insertion  is 
that  they  are  covered  first  with  the  opaque  capsule  of  Tenon 
which  covers  the  sclera  to  within  3  nun.  of  the  sclero-cor)U'al 
margin  and  over  this  on  the  outside  is  the  ocular  conjunctiva. 

Whenever  an  operation  for  strabismus  is  necessary  the  sur- 
geon must  first  make  an  incision  through  both  the  conjunctiva 
and  the  capsule  before  he  can  get  to  the  muscle. 

Most  of  the  pictures  shown  in  the  books  are  rather  mislead- 
ing in  making  the  width  of  the  insertion  of  the  recti  muscle 
appear  rather  narrow.  The  proper  physiological  function  of 
the  extrinsic  muscles  is  to  maintain  fusion  and  therefore 
stereoscopic  vision  at  any  and  all  distances. 

Action. — No  one  of  the  muscles  of  the  individual  eye  acts 
singly,  but  in  groups  of  two  or  more  as  shown  in  the  following 
table : 

Upward  Superior  rectus  and  inferior  ob- 
lique 

Downward   Inferior  rectus  and  superior  ob- 
lique 

luAvard    - Internal  rectus  and  superior  and 

inferior  oblique 

Outward  External  rectus  and  superior  and 

inferior  oblique 

Upward  and  Inward Superior  rectus,  external  rectus, 

and  inferior  oblique 

Upward  and  Outward Superior  rectus,  external  rectus, 

and  inferior  oblique 

Downward  and  Imvard Inferior  rectus,  internal  rectus, 

and  superior  oblique 

Downward  and  OutAvard Inferior  rectus,  external  rectus, 

and  superior  obliciue 


66  Ki-:tciiu.m's  Lessons  ox  the  Eve 


THE  REFRACTIVE  MEDIA. 


Ill  oi'dor  that  an  eye  may  sec  (listiiiclly  it  is  iiecessai'v  that 
the  vibrations  of  light  that  come  from  ditferent  distances  out- 
side of  the  eye  be  enaliled  to  reach  the  inside  coat  called  the 
retina.  In  doing'  this  they  ])ass  through  tlie  Iranspareiit  ])()r- 
tioiis  viz.:  cornea,  aqueous  humor,  lens,  vitreous  humor.  All 
of  these  together  act  as  one  piece  of  mechanism  and  are  called 
the  refractive  media  because  the  word  refraction  means  to 
change  and  adjust  rays  of  light  from  one  direction  to  another, 
and  so  these  four  parts  act  as  the  medium  for  properly  adjust- 
ing the  forms  of  light  that  enter  the  eye. 

Aftei-  extended  study  of  what  are  considered  to  be  normal 
eyes  a  certain  positive  "valuation  of  adjustment"  has  been 
given  to  this  refractive  media  in  terms  of  dioptres  and  is 
called  the  dioptric  pov^er  of  the  eye.  A  Dioptre  is  the  unit  of 
measurement  for  optical  lenses.  lD.=a  focus  of  ])ara]l('l  rays 
at  1  metre  from  the  lens;  2D.=y2M.  focus.  Now  looking  at  it 
another  way  we  would  say  a  lens  that  focuses  at  OI.  is  a  ID. 
lens;  at  y^M.  a  2  D.  lens;  consequently  after  this  manner  the 
dioptric  power  of  the  eye  was  figured  out. 

Tscliei'iiing  in  his  "  IMiysiologic  Ojitics,"  ])age  :U.  gives  the 
dioptric   \alue   of  1h<'   complete   optic   system   of  the   eye   to 

l)e  58.:^^. 

The  cornea  about  421).  and  the  Umis  KiD.  The  aipieous  and 
vitreous  humors  liaving  but  littb-  vabie  in  the  sum  total. 
Authoi's  differ  but  littlr  on  tlirsc  points  so  it  is  (|uit(>  safe  to 
sav  that  aliont  (iOD.  is  the  dioptric  i.owri'  of  the   fully  devel- 


Ketciium's  Lessons  on  the  Eye  67 


A  STUDY  OF  ACCOMMODATION. 


Accommodation,  in  the  study  of  the  eye,  means  in  effect,  a 
change  in  the  arrangement  of  the  rays  of  light  after  entering 
the  eye,  so  tliat  whether  close  to,  or  at  some  distance  away 
from  the  eye,  the  object  looked  at  must  be  kept  "focused" 
or  sharply  defined  upon  the  retina.  This  change  takes  place 
only  in  the  lens,  not  by  sliding  backward  and  forward  as  in 
adjusting  a  telescope ;  but  merely  by  changing  the  adjust- 
ment of  the  lens  from  its  least  convexity  and  in  this  way  in- 
creasing or  decreasing  its  dioptric  power. 

In  the  study  of  Ophthalmic  Optics  and  the  practice  of 
Optometry  it  becomes  necessary  for  the  student  to  realize  the 
importance  of  this  subject. 

Two  special  points  are  always  to  be  considered: 

(1)  Conjugate  foci;  (2)  Amplitude  and  range  of  accom- 
modation. 

A  great  deal  of  study  has  been  given  in  an  experimental 
way  as  to  just  how^  the  "Act  of  Accommodation"  is  accom- 
plished and  the  most  satisfactory  and  acceptable  action  of 
the  eye  is  as  folloAvs : 

(1)  Parts  concerned  are — The  lens  and  the  suspensory 
ligament  and  ciliary  muscle  Avhich  directly  surrounds  it. 

(2)  Action — The  contraction  of  the  ciliary  muscle  nar- 
rows the  little  space  around  the  edge  of  the  lens  Avhich  has 
been  held  taut  by  the  suspensory  ligament  which  is  attached 
to  it,  thus  releasing  the  tension  on  the  lens,  Avhich  being  some- 
what elastic,  increases  in  convexity  according  to  the  neces- 
sity of  regulating  the  light  so  that  it  focuses  on  the  retina 
properly.  The  relative  distance  the  eye  is  from  the  object 
desired  to  be  seen  is  the  governing  influence  impelled  by  the 
brain  to  adjust  it  for  that  particular  point. 


68 


Ki:tc hum's  Lkssoxs  ox  the  Eve 


According  to  scientific  tests  of  many  thousands  of  human 
eyes  as  regards  vision  it  is  a  fact  that  -wlien  one  is  twenty 
feet  or  more  away  from  any  object  he  is  looking  at  that  no 
accommodation  is  necessary  at  any  age,  in  the  perfect  eye, 
in  oi-der  to  see  plainly.  Here  the  eye  is  said  to  be  at  rest — 
meaning  no  acconnnodation  or  eye  strain.  According  to 
th<'  ''laAvs  of  light."  however,  at  any  age,  the  adjustment 
(accommodation)  becomes  necessary  Avhen  looking  at  an 
object  at  any  point  closer  than  twenty  feet.  The  closer  the 
o])ject  the  greater  the  demand  for  th(>  adjustment.  This  is 
Avhat  is  termed  conjugate  foci  in  the  sense  that  soim'  one 
])oint  outside  of  the  eye  is  always  in  dii'i^ct  focus  with  the 
retina. 


Range  of  Accommodation 

We  present  here  a  tal)lo  having  reference  to  the  fact  that 
"Accommodation,"  or  the  230wer  to  adjust  the  lens,  decreases 
gradually  as  the  years  pass. 


Amplitude 
Year                           in  Dioptres 

Year 

Amplitude 
in  Dioptres 

]0  

15  

90 

14 

12 

10 

8.5 

7 

5.5 

4.5 

45  

50  

55 

3.5 

2.5 

1.75 

25  

30  

35  

40  

60  

65  

70  

75 

1 

0.75 

0.25 

0.00 

Now  ui)oii  i-efereiice  to  the  table  it  will  be  seen  that  as 
the  lens  becomes  harder  and  less  elastic  by  age,  it  eventually 
entirely  loses  this  power  and  needs  artificial  hel])  in  the  form 
of  glasses  that  will  supply  the  deficiency,  in  early  youth. 
then,  we  find  that  llie  I'ange  or  adjustment  of  aeeoniuiodation 
is  the  greatest,  and  that  is  why  glasses  become  necessary  for 
feasy  close  w^ork  at  about  forty-five  years  of  age,  and  tluMv- 
after  an  occasional  change  to  a  strong»f  focus  is  lu'eded  to 
keep  pace  with  the  gradual  loss  within  the  eye. 


Kktciium's  Lesson's  ox  the  Ev 


69 


SHOWING  CHANGES  IN  ACCOMMODATION 


Ciliary  muscle 


Even  though  one  may  know  the  anatomy  of  the  parts  involved  in 
accommodation,  still  it  is  sometimes  difficult  to  grasp  just  what  does 
take  place.  The  two  diagrams  here  shown  will,  serve  to  make  it  more 
clearly  understood.  Remember,  the  diagrams  are  flat  views  and  the 
student  must  always  have  in  mind  that  he  is  facing  the  front  of  the  eye; 
that  the  ciliary  muscle  and  suspensory  ligament  surround  the  edge  of 
The  lens;  that  the  lens  is  at  its  least  convexity  as  shown  on  the  shaded 
part  of  the  one  picture.  Now,  when  the  ciliary  muscle  contracts  it 
draws  closer  to  the  edge  of  the  lens  all  around  it  equally.  The  lens 
then  becomes  thicker  through  its  antero-posterior  diameter.  At  the 
same  time  the  pupil  contracts  a  little  to  sharpen  vision.  A  branch  of 
the  third  nerve  affecting  both  the  ciliary  muscle  and  the  sphincter 
muscle  of  the  iris  act  at  the  same  time.  Such  a  change  is  constantly 
going  on  as  a  person  changes  his  view  from  one  point  to  another. 


Ki:r(iirM"s  Lessons  ox  the  Eve 


A  study  of  Accomraodation. 


Change  in  the  curvature  of  the  lens  in  accommodation  according 
to  the  theory  of  Helmholtz. —  (Modified  from  Landolt.) 


Ketchum's  Lessons  on  the  Eve 


SPASM  OF  ACCOMMODATION. 


This  term  represents  the  ''live  wire"  of  the  majority  of 
complaints  that  are  classed  under  the  condition  called  "eye- 
strain." It  is  the  fighting  line  between  the  oculist  and  the 
optometrist.  It  is  the  home  office  of  trouble  for  the  refrac- 
tionist  who  doesn't  thoroughly  vmderstand  its  little  game  of 
deception.  It  is  the  thing  that  really  put  optometry  on  the 
map  Avhere  it  is  today.  It  is  the  thing  that  demands  lots  of 
respect  and  attention.     Study  it. 

Getting  doAvn  to  facts.  Spasm  of  acconnnodation  means  a 
tired  ciliary  muscle  resulting  from  an  excessive  demand  upon 
it  to  adjust  and  maintain  more  perfect  vision  which  it  be- 
comes necessary  to  do  when  some  departure  from  normal 
vision  exists  in  the  eye.  A  tired  muscle  cramps  or  contracts. 
When  the  ciliary  muscle  is  tired  it  manifests  the  fact  by 
causing  distress  in  various  ways.  Knowing  that  contraction 
of  this  muscle  is  what  adjusts  the  focal  power  of  the  lens, 
the  student  will  at  once  realize  that  the  nerve  force  used  is 
compelled  to  act  beyond  its  normal  capacity  and  must  finally 
become  more  or  less  inefficient.  Such  is  the  case  with  vary- 
ing symptoms  of  this  disorder.  It  being  partial  at  times 
called  clonic  spasm  and  again  mor(>  or  less  permanent  called 
tonic  spasm.  AVhen  the  oculist  finds  such  a  condition  ap- 
parently manifest  he  uses  "drops"  called  a  Cycloplegic  which 
releases  the  cramped  condition  of  the  ciliary  mufccle  and 
enables  him  to  get  the  exact  refraction  of  the  eye  very 
readily.  Being  a  physician  he  is  legally  entitled  to  use  drugs 
according  to  his  best  judgment.  The  use  of  such  drops  has 
its  inconveniences  and  draw-backs.  Necessity  demanded  a 
different  procedure  that  ultimately  Avould  attain  the  same 
results.  After  years  of  experimenting  Avith  Ophthalmic 
lenses  a  veiy  satisfactory  method  has  l)een  developed  called 
the  fogging^  system,  also  an  entirely  different  method  called 
static  and  dynamic  skiametry  ot'  retinoscopy.  It  is  by  the 
use  of  these  two  methods  that  the  ()])t(mieti'ist  is  able  to  com- 
pete with  the  oculist  and  satisfy  his  patients. 


Kiii'c  iu-m's  Lkssoxs  on  the  Eye 


PART  THREE 

pfesciils    ill 

simpl 

e    form   the    sort 

of   p 

ithologieal 

conditions 

of  the 

eye  that  any  refractionist  s 

lould 

l)e  familiar 

with. 

The  Optometris 

t  has 

his  li 

mita- 

tions  and  s 

honld 

al:)solutely  know 

them. 

His 

per- 

sonal  wolf; 

re  aiK 

that   of  his   patient   must 

it   all 

times  be  re 

el\one( 

Avitli.     Let  your 

mott( 

be  ' 

'Play 

Safe." 

Now    til  a 

t    you 

ha\e    become    fa 

miliar 

witl 

1     the 

aiiatoniy,  ]i 

li  ysioh 

jiy   and   o])tics   o 

llie 

'\  e   i 

will 

])r()ve   an    e 

asy  matter  1o   aO(juire   ; 

11(1   li. 

)1(1   a 

tiood 

working'  k 

lowled 

^f   of  diseased    C( 

ii(li1i( 

Ketchum's  Lessons  on  the  Eve  7Z 

DISEASES   OF   THE   EYE   THE  OPTOMETRIST   SHOULD 
RECOGNIZE 

Every  refractioiiist  before  taking  the  first  step  toward  the 
regular  examination  for  glasses  should  look  carefully  for  any 
unusual  sign  or  symptom  of  the  eye  bearing  upon  any  past 
or  present  condition  that  would  be  likely  to  interfere  with 
successful  completion  of  his  work.  During  the  inspection  he 
should  ask  the  patient  if  at  any  time  he  has  had  any  diseased 
condition  of  the  eyes  of  a  serious  nature,  as  there  might  be 
some  internal  disease  that  he  should  know  about. 

Any  acute  inflammatory  condition,  sometimes  even  with 
apparently  trivial  symptoms  may  cause  photophobia  and 
ciliary  spasm  and  interfere  materially  Avith  exact  work. 

The  list  given  here  is  merely  intended  as  a  synopsis  that 
will  convey  a  quick  understanding  of  the  conditions  men- 
tioned and  lead  to  a  text  book  on  Eye  Diseases  for  a  more 
complete  knowledge. 

EXTERNAL  DISEASES 

CONJUNCTIVITIS— The  palpebral  conjunctiva  lines  the 
lids  back  to  the  fornix  where  it  turns  back  upon  the  ball  and 
becomes  the  ocular  conjunctiva  from  there  forward  to  the 
margin  of  the  cornea. 

Of  course  in  all  acute  stages  of  diseased  conditions  one 
can  refract  only  those  of  more  or  less  mild  form,  if  at  all. 

Simple  conjunctivitis  is  merely  an  irritable  conjunctiva 
Avhich  occurs  from  many  causes  including  eye  strain.  There 
is  no  discharge  of  pus,  but  more  or  less  increase  of  redness 
especially  of  the  inside  of  the  lids.  Photophobia.  Even  if 
you  fit  glasses  under  such  conditions  the  patient  may  return 
to  say  they  are  not  satisfactory,  when  the  Avhole  complaint 
would  really  be  caused  by  the  condition  of  the  lids. 

TRACHO]\IA  or  GRANULATED  LIDS.— This  is  chronic 
inflammation  of  the  conjunctiva — always  photophol)ia — and 
nearly  always  haziness  of  the  upper  third  of  the  cornea,  called 
Pannus.     You  cannot  refract  satisfactorily. 

PTERYGIUM — is  a  fan-shaped  growth  of  the  conjunctiva 
extending  from  the  inner  canthus  to  the  edge  and  sometimes 
upon  the  nasal  side  of  the  cornea.  It  interferes  with  satis- 
factory refraction  and  should  be  removed  by  operation. 


74  Kktchum's  Lessons  ox  the  Eve 

PINGUECULA— is  a  small,  fatty  deposit  in  the  sclera  be- 
tween the  cornea  and  the  inner  canthus.  It  is  not  a  disease, 
no  harm  comes  from  it,  leave  it  alone. 

CIIALAZIOX — -Sub-acnte  tumor  of  one  or  more  of  the 
]\reibomian  Glands  in  either  the  upper  or  lower  lid.  Xo  pain, 
usually  grows  larger  in  time  and  interferes  with  good  visual 
acuity  by  jDressing  on  the  eye-ball  and  distorting  everything 
seen.  Cannot  refract  very  satisfactorily  on  that  account. 
Advise  operation. 

liLEPIIARTTTS— Thickening  of  the  edges  of  the  lids  by 
inHammatory  process  or  eye  strain.  Small  scales  at  the  roots 
of  the  cilia  and  sometimes  pimples,  patients  nearly  always 
astigmatic.  Eefraction  not  always  satisfactory  until  cured 
by  treatment. 

HORDEOLUM — Common  stye,  very  painful,  often  the  re- 
sult of  eye  strain. 

EXTROPIOX— Edge  of  the  lid  turns  in— is  the  result  of 
injury  of  chronic  disease  of  the  lids  causing  the  cilia  to  rub 
against  the  eye-ball. 

ECTROPIOX — same  cause  as  Entropion — edge  of  lid  turns 
away  from  the  eye-ball.  Usually  the  lower  lid.  This  con- 
dition results  in  epiphora. 

EPIPHORA— is  an  overflow  of  tears  upon  the  cheek  be- 
cause they  cannot  escape  through  the  puncta  into  the  lachrymal 
canal  on  account  of  obstruction. 

LACIIRYMATIOX— is  a  term  used  to  denote  an  excessive 
flow  of  tears  from  emotional   causes.     Xo  ohst  ruction. 

\IOr>ULA — is  an  almost  im|)ercei)til)le  ha/iness  of  nil  or  a 
small  ])art  of  the  cornea. 

^lACULA — is  a  small  sjxd  or  ()])acit\'  of  Ihe  cornea,  usually 
of  the  two  anterior  laxcis. 

LEUCO^NIA — is  a  dense  opacitx-  of  the  cornea  in  ])nit  or  in 
whole  and  usuall\-  the  r(>snlt  of  n  sei-ious  injury  or  disease 
that    alTeels  the  true  corneal   la\(M-. 

PA.\.\rS-  is  a  well  deliiied  ha/iness  usually  found  in  the 
upper  Ihii'd  of  tlm  cornea,  usually  the  result   of  Trachoma. 


Ketch u MS  Lessons  on  the  Eye  75 

FOREIGN  BODY  IN  THE  EYE.     (abbreviated  F.  B.) 

This  means  anything  at  all  that  finds  its  way  between  the 
lids  and  remains  there,  whether  loose  or  attached. 

Where  this  directly  concerns  the  Optometrist  is,  that  it 
occurs  very  frequently  that  a  person  will  call  upon  a  refrac- 
tionist  anticipating-  relief  from  some  recent  eye  trouble  and 
demanding  glasses  for  it.  Inquiry  discloses  the  fact  that 
within  the  past  few  days  more  or  less  irritation  with  some 
pain  has  developed  in  one  eye  only.  A  well  informed  refrac- 
tion ist  must  at  once  conclude  that  it  is  not  a  case  of  eye 
strain.  I^pon  careful  inspection  in  such  cases  under  a  good 
light  ])y  oblique  illumination  a  minute  spot  will  be  seen  on 
the  cornea,  that  does  not  belong  there.  If  gray  in  appear- 
ance it  is  likely  to  be  a  small  ulcer.  If  dark  it  is  without 
doubt  some  small  particle  that  has  become  imbedded  in  the 
anterior  layers  of  the  cornea  and  should  be  removed.  In 
either  case  don't  touch  it  as  it  is  a  case  for  the  medical  doctor. 
It  is  just  as  liable  to  occur  soon  after  you  have  fitted  that 
person  with  glasses  and  if  so  you  will  be  the  first  person 
thought  of  and  the  blame  given  to  you,  so  ])e  careful  to  watch 
out  accordingly. 

CORNEAL  ULCER. 

Very  painful,  photophobia  intense,  lachrymation  profuse, 
palpebral  and  ocular  conjunctiva  inflamed.  Inspection-  will 
show  a  small  gray  spot  on  the  cornea.  It  must  have  imme- 
diate and  skillful  attention,  as  if  in  front  of  the  pupil  it  may 
result  in  partial  blindness  in  that  eye. 

PTOSIS — Drooping  of  the  uj^per  lid.  Usually  congenital 
owing  to  incomplete  development  of  the  levator  palpebrarum 
muscle.  Operation  does  no  good.  If  acquired,  it  is  usually 
the  result  of  acquired  syphilis  and  means  a  partial  paralysis 
of  the  third  cranial  nerve.  Consequently  all  that  the  third 
nerve  supplies  is  affected  and  we  have  cycloplegia-mydriasis 
with  the  cornea  turned  down  and  toward  the  outer  canthus 
owing  to  the  muscles  being  unable  to  hold  it  in  the  pi'imary 
position  and  leaving  it  under  the  control  of  the  external 
rectus  and  superior  oblique. 

ECCHYMOSIS— ''Black  eye,"   result  of  injury. 

TRICHIASIS— "Wild  Hairs"  or  eyelashes  usually  turning 
in  and  rubbing  upon  the  eye-ball  causing  much  distress,  oper- 
ation necessary  for  relief. 


Ketciu'm's  Lessons  ox  i  iik  Eve 


INTERNAL  DISEASES 


IRITIS. 

Acute  Iritis  is  vei-y  ])aiiiful.  Four  ])rinci|)al  symptoms  are: 
pain,  contracted  pupil,  iris  looks  dull,  redness  on  the  sclera 
around  the  cornea.  Usually  caused  by  syphilis  or  rheu- 
matism. If  not  promptly  and  properly  treated  and  the  pupil 
widely  dilated,  the  posterior  surface  of  the  iris  becomes  at- 
tached to  the  l(Mis  capsule.  Once  such  a  condition  is  estab- 
lished called  posterior  synechia  the  result  is  that  the  pupil 
Avill  not  react  to  lijiht  and  also  the  lens  has  lost  its  adjust- 
ment for  accommodation  and  becomes  static.  In  such  a  con- 
dition it  is  out  of  the  question  to  satisfactorily  refract  such 
an  eye  on  account  of  havino-  no  Avay  to  adjust  the  focus.  The 
Avay  to  detect  the  extent  of  the  adhesions  is  to  have  a  physician 
use  a  mydriatic. 

Anterior  synechia  is  a  term  applied  where  the  front  part 
of  the  iris  has  beconu'  attached  to  some  part  of  the  inside  sur- 
face of  the  cornea,  the  result  of  disease  or  injury.  Such  a 
condition  can  plainly  be  seen. 


OPTIC  ATROPHY. 

Tile  sul)jce1i\-e  symi)1oiiis  are  I'cduelioii  in  the  aeuteness 
of  vision  both  as  to  color  and  form,  Avith  more  or  less  dila- 
tion of  the  pupil — (mydi-iasis).  Complete  blindness  is  the 
usual  i-e.sult  of  the  pj'0}>i"ess  of  this  diseas(\  Ilavino-  studied 
and  become  familiar  with  the  appearance  of  the  o]itic  disc  in 
health  the  examiner  will  (juickly  notice  the  loss  of  its  ])inkish 
zone  as  well  as  its  minute  vessels  Avhich  have  disajipeared  leav- 
ing- the  entire  disc  presenting'  a  dull  white  ai^jieaiance,  Avhile 
the  blood  vessels,  es])ecially  the  arteries  of  the  retina,  are 
much  smaller  than  usual.  Thr  ball  letains  its  normal  tension 
and  the  refractive  media  char.  i1  is  by  this  compai'ison  that 
it  is  easy  to  dislinyuish  belwcen  iilaueoma  and  oi)tic  ati'o]ihy. 
I1  eliicflv  oeenrs  in  middle  lil"e  and  llicic  is  really  no  sueeess- 
fnl    Ireaimrnt. 


Ketchum's  Lessons  on  the  Eye  17 

EVERY  REFRACTIONIST  SHOULD  KNOW  SOMETHING 
ABOUT  CATARACT 

CATARACT  is  any  complete  or  partial  opacity  of  the  lens 
or  its  capsule.  There  are  three  general  terms  that  cover  all 
conditions : 

Congenital, 

Tranmatic, 

Senile. 

The  term  "congenital"  implies  present  at  birth.  In  many 
children  directly  after  birth  is  found  more  or  less  opacity  of 
the  lens  which  condition  will  remain  stationary  throughout 
the  life  of  that  person.  A  slight  opacity  admits  light  into  the 
eye  and  the  actions  of  a  child  thus  afflicted  simulates  myopia. 
The  only  remedy  is  surgical. 

TRAUMATIC  CATARACT.  The  term  ''traumatism"  means 
injury.  Anyone  at  any  age  can  be  thus  afflicted.  A  blow 
directly  upon  the  eye-ball  will  cause  it.  If  the  capsule  is  not 
ruptured  it  will  become  a  permanent  opacity.  If,  however, 
a  small  rupture  of  the  capsule  occurs  permitting  the  lens  sub- 
stance to  come  into  contact  Avith  the  aqueous  humor,  the  latter 
gradually  absorbs  it,  the  debris  being  carried  off  through 
Schlemm's  canal. 

SENILE  CATARACT  is  comparatively  common  and  likely 
to  develop  in  anyone.  It  usually  appears  after  the  age  of 
fifty.  The  real  and  direct  cause  in  any  given  case  is  unknown 
other  than  we  know  that  some  interference  has  taken  place 
wdth  the  nutrition  of  the  lens  usually  supplied  by  the  ciliary 
processes  and  the  lymph  in  Petit 's  canal.  Some  cases  are 
traceable  directly  to  some  general  disease  such  as  Diabetes, 
Bright 's  Disease  of  the  kidneys,  Arterial  disease,  etc. 

Symptoms. — There  is  no  pain  nor  inflammatory  condition 
present.  The  first  sign  is  usually  diminished  acuity  of  vision. 
The  patient  complains  of  seeing  spots  on  the  object  looked  at. 
The  interference  with  vision  gradually  increases  until  finally 
there  is  only  mere  perception  of  light.  In  almost  every  in- 
stance only  one  eye  is  aft'ected  at  first  and  progresses  to  quite 
an  advanced  stage  before  the  other  eye  shows  any  symptoms 
Avhatever.  It  is  almost  inevitable,  however,  that  the  fellow 
eye  will  follow^  the  same  course  in  due  time.  The  time  re- 
quired for  full  development  is  very  uncertain.  It  may  be  very 
slow  or  may  ripen  completely  within  a  few  months,  or  it  may, 
at  a  certain  stage  become  stationary. 


78  Ketciium's  Lessons  ox  the  Eye 

There  are  four  stages  of  (Icvplopiuciil   in  senile  cataract: 

lncii)ioiit, 

.M;i1iii-iiiti-  s1a<rc, 

.Mature  or  I'ipe, 

Hyper-mature  or  ovei'  ri])e. 

The  Incipient  or  l)e^inninji'  condition  is  a  more  or  less 
ne])iilous — sliijhtly  opa(|iie — dull  appearauce  of  the  lens  in 
which  the  patient  feels  rather  than  sees  there  is  something 
wrong.  AVith  a  good  light  reflected  by  a  retinoscope  into  the 
eye  it  can  be  det(^cted  l)y  the  observer,  especially  when  com- 
pared with  the  "reflex"  of  the  othei-  eye.  Sometimes  this 
slightly  opaque  condition  I'emains  stationary  foi-  years,  Avith 
compai-ativcly  lilllc  loss  of  useful  vision.  Hence  it  is  often 
wise  not  to  alaim  the  patient  about  if,  but  for  your  own  pro- 
tection an  interested  relative  should  be  informed  accordingly. 

The  maturing  stage  comes  next. 

The  vision  is  becoming  noticeably  less  acute  as  the  oi)acity 
increases.  Swelling  of  the  lens  increases  owing  to  absorbing 
fluid  between  its  layers.  The  patient,  at  this  stage,  requires 
less  plus  for  reading  due  to  increased  convexity  of  the  lens 
of  the  eye.  The  condition  is  popularly  known  as  "second 
sight"  and  sometimes,  in  (|uite  an  elderly  person  especially, 
remains  stationary  for  flic  balance  of  his  life. 

The  third  stage  means  ripe  cataract.  The  eye  has  become 
blind  owinii-  to  complete  opacity  of  the  lens,  and  its  appear- 
ance now  is  a  dull  ti'ray  or  slightly  amber  coloi'.  It  has  lost 
the  lluid  i)icvi()us]y  absoi-bed.  Hs  many  layei's  have  become 
(irmly  adhei'ed  to  one  anoHier  and  it  is  at  this  period  that  it 
is  most  easily  se])a rated  from  its  capsule  and  for  best  results 
should  l)e  removed  withoul  much  delay  as  furflnn-  chanjues 
ai-e  likely  to  develop  into  Ihe  hyper-mature  slatie,  and  an 
()|)ei'afion  upon  over-ri]ie  ealaracf  is  less  fa\'oral)lc 
diflieull    Ihan  durinti'  1li«'   iiialuiv    period. 


more 


AN  APHAKIAL  EYE 

is  an  eyr  willioul  a  Ims,  usually  Ihe  rcsuH  of  an  injury  or 
o])ei'ati()n.  Sueli  a  couditioii  can  usually  be  delreled  l>\  no- 
ticing' llial  Ihe  pupil  dips  haekward  instead  of  forward  and 
the  iris  is  tremuhuis  (if  shakes  as  the  eye  is  uH>\cd  ahonl. 
owiu'j  1o  Ihe  suppnri  uf  the  leiis  which  was  direetl\  behind 
jiiid    ill    contact    with    it    liaxinu    heeii    taken    awa\. 


Ketchum's  Lessons  on  the  Eye  79 

The  usual  spherical  lens  to  correct  infinity  for  an  aphakial 
eye  is  about  a  plus  10.  Usually  a  plus  cylinder  against  the 
rule  is  required  also.  By  no  means  is  it  usual  to  expect 
good  vision  in  such  cases  and  it  is  considered  excellent  results 
if  fifty  per  cent  vision  is  regained  after  a  catai'act  operation. 
About  plus  three  added  to  the  distance  lenses  is  lequired  for 
close  Avork. 


GLAUCOMA 

This  is  an  important  and  very  serious  disease  of  the  eye 
that  every  refractionist  should  be  on  the  lookout  for,  espe- 
cially in  people  somewhat  advanced  in  years.  When  an  eye 
is  once  afflicted  with  this  disease  very  little  can  be  done  for 
it  in  the  way  of  permanent  relief.  I  can  merely  refer  to  it 
in  a  general  way  and  strongly  urge  the  student  to  study  it 
carefully  in  some  text  book  on  diseases  of  the  eye.  The  reason 
why  one  should  know  how  to  detect  it,  is  that  in  the  majority 
of  cases  in  which  it  is  developing  it  is  found  that  the  hereto- 
fore acuity  of  vision  of  the  patient  is  gradually  becoming  less 
and  he  comes  to  you  with  all  confidence  expecting  relief  from 
glasses.  A  relief  Avhich,  properly  speaking,  you  cannot  give 
him.  It  ultimately  means  complete  blindness  with  no  prob- 
able hope  for  a  cure.  If  so,  then  can  you  not  do  as  much  for 
the  patient,  with  glasses,  as  can  the  Oculist?  You  can,  of 
course.  But  the  Optometrist  must  always  bear  in  mind  that 
he  is  not  to  be  considered  as  ''the  court  of  last  resort"  in  a 
legal  or  properly  qualified  sense  and  in  no  case  should  assume 
any  responsibility  for  suspected  pathological  conditions. 

One  special  symptom  to  become  familiar  with  is  the  "ten- 
sion" of  the  eye-ball.  First  learn,  by  lightly  pressing  with 
the  forefinger  of  each  hand  upon  the  healthy  eye-ball,  its 
"give  and  take"  feeling.  Glaucoma  being  a  condition  where 
the  drainage  of  the  debris  from  the  eye  through  the  spaces 
of  Fontana  and  canal  of  Schlemm  has  become  retarded,  the 
eye-ball  gradually  becomes  more  tense  or  hard  until  finally  it 
is  a  very  easy  matter  to  detect  that  fact  by  palpation  with 
the  finger  tips. 


80  I\i:Tcrir>r's  T.r.ssoxs  ox  tiif.  Eve 


FLOATING  SPOTS  IN  THE  EYE 


Very  often  the  refractionist  will  have  patients  who  com- 
plain of  the  facl^  that  "every  once  in  awhile  I  have  little  spots, 
like  shadows,  in  my  eyes  and  they  appear  to  move  around 
when  I  move  my  eyes,  but  settle  down  and  are  quiet  when  I 
am  reading  or  writing.  There  isn't  any  pain  about  it  but 
they  annoy  me  and  I  would  like  to  know  what  is  wrong." 
This  condition  is  knoAvn  as 

Muscae  volitantes  or  floating  particles  in  the  vitreous. 

You  will  state  to  the  patient  "that  in  most  cases  they  do 
not  mean  any  harm  as  far  as  disease  is  concerned ;  but  are 
usually  the  result  of  eye-strain,  insomnia,  indigestion,  etc. 
All  of  which  must  be  looked  after  and  remedied  accordingly." 
In  myopia  of  high  degree,  floating  specks  are  almost  constant 
and  are  not  always  relieved  by  Avearing  glasses. 

Having  now  given  a  general  description  of  the  principal 
external  and  internal  diseased  condition  of  the  eyes  that  it 
is  the  duty  of  the  Optometi-ist  to  recognize  in  order  to  "play 
safe"  l)oth  to  himself  and  his  confiding  patient,  Ave  leave  this 
thought  with  him  :  That  no  person  is  entirely  his  -own  patient 
who  in  any  Avay  is  afflicted  with  even  the  slightest  pathoK)g- 
ical  disturbance.  An  apparently  simple  symptom  might  and 
often  does  lead  to  serious  results  if  not  promptly  recognized 
and  cared  for.  A  careless  diagnosis  with  an  ignorant  prog- 
nosis mav  lend  to  troulile.  Do  not  often  advise  nor  assume 
anv  responsibilitv.  KKFER  THE  CASE  AT  ONCE  TO  THE 
OPHTHAl.lMOLOrilST. 


Ketciium's  Lessons  ox  the  Eve  81 


NYSTAGMUS 


Occasionally  someone  will  call  upon  you  to  see  if  you 
can  benefit  their  vision  with  glasses.  Upon  the  usual  in- 
spection (always  necessary  before  proceeding  with  the  Optical 
examination)  you  discover  a  peculiar  and  constant  lateral 
twitching  of  both  eyes.  You  have  a  case  of  genuine  nystag- 
mus. There  are  varieties  of  the  movements  classified  under 
this  head ;  but  generally  we  find  the  movements  or  twitching 
of  the  eyeballs  are  rhythmic  bilateral  and  from  side  to  side; 
both  to  the  right,  then  to  the  left,  and  so  on,  averaging  in  speed 
from  one  to  three  times  in  a  second  and  to  the  extent  of  about 
two  or  three  mm.  to  either  side  of  the  primary  position  straight 
ahead. 

This  condition  is  usually  congenital  and  with  an  obscure  eti- 
ology (cause.)  Sometimes  it  is  the  result  of  some  serious  ejec- 
tion of  the  eyes  soon  after  birth,  resulting  in  corneal  scars  that 
prevent  the  "development  of  good  vision.  Congenital  cataract 
is  also  a  contributing  feature.  When,  however,  the  refractive 
media  is  clear  the  condition  of  suspended  development  is 
rather  difficult  to  discover.  Anyway,  it's  not  your  case, 
because  of  the  fact  that  it  has  been  found  that  glasses  offer 
very  little  help  in  the  way  of  improving  vision.  True  nystag- 
mus is  not  due  to  Optical' defect  and  is  not  traceable  to  occu- 
pation. No  perfectly  satisfactory  explanation  of  nystagmus 
has  yet  been  given,  other  than  it  is  a  perversion  of  the  centres 
for  parallelism  and  not  with  the  muscles  themselves. 


82  Kktciium's  Lessons  ox  the  Eye 


AMBLYOPIA 


Strictly  spcakiiio-,  amblyopia  is  not  disease  in  any  form. 
AVe  classify  it  here  because  the  text  books  do  not  explain  the 
term  in  a  way  to  make  it  thoroughly  understood  by  the  non- 
medical rafractionist.  Its  real  meaning  is  as  folloAvs,  viz.: 
Diminished  visual  acuity,  congenital,  Avith  no  possible  remedy. 
The  eye  is  not  blind  nor  diseased  in  any  form.  In  no  sense 
is  true  amblyopia  an  acquired  condition.  The  refractive 
media  is  clear  and  may  or  may  not  be  ametropic.  Notwith- 
standing correct  retinoscopic  findings,  the  glasses  do  not  ma- 
terially improve  vision  then  or  thereafter.  The  ametropia  in 
an  amblyopic  eye  may  be  exactly  the  same  as  in  the  fellow 
eye  which  sees  perfectly  with  its  correction  by  glasses,  while 
the  former  will  not.  The  Ophthalmoscope  or  any  other  kind 
of  an  objective  examination  shows  nothing  wrong.  What  is 
the  answer?  Simply  this:  At  one  or  more  points  from  and 
including  the  retina  to  and  including  the  optic  tract  there  is 
an  interference  with  the  proper  vibrations  of  light  that  have 
reached  the  retina,  and  an  undeveloped  condition  of  some 
unknown  kind  exists  that  obtunds  detail  in  objects  and  gives 
only  a  gross  image  in  return.  If  for  any  reason  the  develop- 
ment of  rods  and  cones  does  not  continue  after  birth  the 
vision  remains  accordingly.  Microscopical  study  of  the 
retina  shows  about  8,500,000  cones  in  the  I'etina  at  birth ;  and 
in  the  fully  developed  eye  about  7,000,000.  In  the  macula 
alone,  a  space  of  less  than  2  mm.  in  dianider.  Iliere  are  in 
tho  developed  eye  1;M)()0  eones.  Tlow  ]>lainl\-  tlicn.  is  the  fact 
1lia1  in  any  condition  wlicic  llic  eoncs  arc  less  lliaii  Ihe  amount 
re(|iiir(Ml  foi-  u'ood  vision,  1  lie  eye  cannol  he  made  subject  to 
decided  iniprovemeiil.  Also  i1  must  be  renienib.Ted  that  the 
optic  ti'ael  re|)i-esen1s  a  '•enlli\a1ed  area""  thai  is  developed 
only  in  aeeoi-danee  willi  llie  demand  made  npon  i1  llii-ongh 
llie   icfraelive   media. 

A  diaunosis  of  aiiibl  \ opia  is  made  only  by  "  exelnsion  ; "' 
meaning  a  llioroniib  faniiliarily  of  all  the  ()])tical,  i)liysiolog- 
ical    and   pal liolotiieal    conditions  of  the  eye,  and   after  eare- 

fnllv-    cxjimininu    for   all    an.l    eliniinaling   tliem    from    the   ease 
we  "li;iv<>    onlv    one    i)rol);ddc    condilion    \r\'\    !lia1     in    any    way 


Ketch um's  Lessons  on  the  Eye  83 

answers,  so  it  must  be  amblyopia.  Tlieie  nw  oIIht  condii  ions 
of  (liminish(Hl  vision  tliat  simulate  true  amblyopia  tluil  in 
our  examination  we  find  are  false.  They  are  classed  as  fol- 
lows, viz. : 

1.  And)lyopia  Exanopsia. 

2.  Amblyopia  Toxic. 

3.  And)lyopia  Hysterical. 

No.  1  is  diminished  visual  acuity,  the  direct  result  of  un- 
corrected ametropia  ;  and  owing  to  want  of  o]itic  tract  train- 
ing, does  not  immediately  and  fully  respond  to  tlie  coiTCct 
glasses.  If,  hoAvever,  the  glasses  ai-e  woi'ii  continually  for 
some  time  there  is  a  gradual  improvement  in  sight  until  after 
a  time  it  becomes  comparatively  normal.  The  history  of  the 
case  differs  somewhat  from  true  amblyopia  as  the  element  of 
a  high  ametropia  is  ahvays  present,  and  the  vision  improves 
with  glasses  while  in  the  true  condition  it  does  not.  The  point 
is,  be  guarded  in  your  prognosis. 

Toxic  amblyopia  is  diminished  vision  ahvays  in  both  eyes, 
the  result  of  auto-intoxication  of  some  form.  It  may  be  from 
over  indulgence  in  food,  liquors,  or  drugs.  Easily  diagnosed; 
and  the  remedy  is  to  cleanse  the  system  and  put  it  into  a 
healthy  condition  after  which  the  eyes  will  resume  the  same 
vision  as  before. 

Hysterical  amblyopia  is  practically  nothing  at  all  the  mat- 
ter Avith  the  eyes.  It  is  regarded  by  many  as  a  sex  problem 
and  treatment  is  directed  toward  the  general  nervous  system. 
In  some  cases  it  is  of  only  short  duration  although  it  may 
continue  for  several  weeks.  Judicious  questions  to  the  ])atient 
will  soon  bring  out  the  true  condition.     Leave  it  alone. 


84  Ki:'i(in:-M"s  T.essoxs  ox  riir.  F,vf. 


PATHOLOGICAL  VARIATIONS  OF  THE  PUPIL 


In  ovovy  case,  before  proceeding'  with  an  examination  for 
glasses  the  eves  should  l)e  carefully  inspected  for  signs  of 
abnornuil  conditions.  This  especially  applies  to  the  pupil  as 
more  often  than  suspected  it  offers  a  very  grave  prognosis 
at  a  time  Avhen  the  affected  person  is  little  aware  that  any- 
thing is  seriously  at  fault  with  him. 

Light  reflex  of  the  pupil  means  that  under  ordinary  con- 
ditions tlu^  pu])il  will  contract  and  dilate  according  to  the 
degree  of  light  to  Avhich  the  eye  is  exposed.  Towards  a  bright 
light  it  should  contract  and  on  turning  away  dilate  more  or 
less.  A  fixed  pupil  never  occurs  in  hoalth\-  individuals  with 
healthy  eyes. 

AVhih^  over  a  dozen  different  terms  are  rec|uired  in  explana- 
tion of  ])upil  reflexes,  those  given  here  arc  the  pi-ineipal  ones: 

1.  Loss  of  Pui)illary  light  reflex  with  retention  of  the  con- 
verg(mce  and  accommodation.  (This  is  Argyll-Eobertson 
pupil.) 

2.  Loss  of  convergence  and  aeeoiiimodntion  and  I'etention 
of  light  reflex   (just  o])i)osite  to  the  Argyll-Robertson    i)Ui)in. 

8.  TiOss  of  pu])illar\-  rellex  for  light,  also  convergence  and 
accommodation    (all    Ihi'ee   alfeeled). 

4.  Abnoi'iiial  miosis  (eontractio)i  of  the  ]Mi])in  wilh  refen- 
tion  of  light  reflex  and  convergence.  The  miosis  1)eing  eansed 
eilhei'  from  abnormal  sf  iiiiulaf  ion  of  1lie  spliincl  er  pupilhuN 
(»r  fi'om   i);iialysis  of  the  dilator  pupillae. 

5.  Alinormal  mydi'iasis  fdilalioii^  witli  rd  eiit  ion  of  con- 
vergence and  lighf   I'cllcx.     Slimulalioii  ol'  llie  dilator  ])U|)ilIae. 

n.      Anisocoria    (dilTci-eiicc   in   size   of   pnpil). 

7.      h'regiilar    form    ol'   pupils. 

'I'll.-    Ol f    sprci.il     iiileiesi     1o    the     re  f  fact  ion  ist     is    the 

Argyll-Robertson  iMipil   (study  it   in  the  text   hooks). 


Ketciium's  Lessons  on  the  Eve  85 

Diagnosis. — Loss  of  the  i)U])i]laiy  li<iht  rcilex,  witli  cither 
contraction  or  nnnlinui  dilation.  IJotli  exes  aie  similarly 
affected  in  the  greater  number  of  cases,  although,  in  some  it 
is  unilateral  for  a  long  time.  Again— the  light  retiex  may  be 
utterly  lost  in  one  eye,  and  only  partly  lost  in  the  other.  This 
light  reflex  is  as  a  rule  permanent,  since  it  occurs  the  greater 
number  of  times  as  an  accompaniment  of  diseases  of  the 
nervous  system  that  are  progressive,  and  it  must  be  distinctly 
remembered  that  it  never  occurs  in  healthy  individuals.  The 
pupil  is  ahvays  uniform  and  should  never  be  confounded  with 
posterior  synechia  in  any  form,  the  latter  being  an  attachment 
of  the  iris  to  the  lens  capsule  resulting  from  iritis. 

Etiology. — While  the  general  scientific  opinion  is  that  quite 
all  cases  of  Argyll-Robertson  pupil  are  due  to  syphilis,  there 
are  probable  exceptions  in  a  small  per  cent,  but  it  is  enough 
to  say  that  a  most  important  symptom  has  been  recognized 
that  leads  to  a  grave 

Prognosis. — Regardless  of  the  apparent  health  of  the 
patient  at  the  time  of  the  examination.  The  fact  that  in  this 
condition  the  accommodation  is  not  interfered  with  there  will 
be  no  trouble  in  refracting  the  eyes  either  for  distant  or  near 
point  glasses,  resulting  in  reasonable  satisfaction. 


86 


Kktciium's  Lessons  ox  thf.  Eye 


OPTICAL  NOMENCLATURE 

(Reprint  from   the  Keystone  Magazine  of  Optometry.) 

Address  by  Professor  Frederick  Before  the  Annual  Convention 

of  the  Michigan  Association  of  Optometrists  at 

Jackson,  Mich. 

Every  profession  that  treats  on  scientific  problems  makes  use 
of  (fjlossaries)  scientific  technical  names,  for  the  purpose  to 
perfect  a  lang-uagv  that  may  be  universally  understood.  Op- 
tometiy  has  such  a  language  made  up  of  words,  roots,  j^refixes 
and  affixes  which  are  derived  from  the  ({i-eek  or  Latin,  and  the 
student  who  makes  these  derivatives  a  study  can,  with  ease, 
unravel  the  meaning  of  words  or  coml)ination  of  Avords,  it  mat- 
ters not  how  comph'x  or  difficult  they  may  appear. 

For  example,  for  "a-chroma-opsia,"  we  look  over  the  lesson 
sheet,  first  column,  for  "a,"  Avhich  signifies  "lacking."  Then 
look  for  "chroma,"  which  signifies  color;  then  look  for  "op- 
sia,"  which  signifies  vision;  therefore,  the  term  "a-chromat- 
opsia,"  meaning  lacking  cohn-  vision,  in  other  words,  color 
blind. 

Again,  for  the  word  an-irida  we  find  "an"  signifies  lacking, 
"irida"  signifies  iris — lacking  iris.  Let  us  now  unravel  the 
com])ination  of  an-iso-coria :  "An,"  lacking;  "iso,"  equal; 
"coi-ia,"  pupil.  Lacking  equal  pupil.  Anti-metr-opia:  "Anti." 
opposite;  "metr,"  measure;  "opia,"  error  of  Tefractioii. 
Thei'cfore,  antimeti'opia,  o])posite  measure  of  refraction,  iiu^an- 
iiig  one  eye  nearsighted,  the  olhei'  farsiglited. 


WORDS,   ROOTS,   PREFIXES,  AND   AFFIXES 


Words 
A,  An, 
Aden 

Amauro 

Ambly 

AntI 

Aqueous 

Argo 


From 


Greek 

f'.reok 
Clrcck 
(Irook 
batin 
Greek 


.Ml 


iiiK 


Prefi.xes,    meanins    "Lacking".      (A-blepsia.) 

(An-iso-metr-opia.) 
Glands,   such  as   tear  glands.      (Dacry-aden- 

itis.) 
To  make  dark  (blind),     (.\main-o-sis.') 
Dull,  dim.     (Aml)ly-oi)ia.) 
Opposite.     (Anti-nietr-oi)ia.) 
Water.      (Aqueous  Humor.) 
Non-use,  out  of  use.     (Arg-ambly-opia.) 


Ketchum's  Lessons  ox  the  Eve 


S7 


Words  From  :\Ieaniiig 

Amplitude  Latin       Fullness,  completeness.     (Amplitude  of 

Accommodation. ) 
Algia  Greek       Pain  or  ache.     (Neur-algia.) 

Ab  Latin        Prefix  meaning  "Away"  or  "From".  (Adduc- 

tion.) 
Ad  Latin        Prefix  meaning  "To"  or  "Toward".     (Adduc- 

tion.) 
Blepharo  Greek      Eyelid.     (Blephar-itis.) 

Blenno  Greek      Mucus  or  pus.     (Hlenno-rrhea.) 

Brach  Greek       Short,  near.     (Brach-metr-opia.) 

Blepsia  Greek      Vision.     (A-blei)sia.) 


Chroma 

Core 

Canthus 

Cata 

Cerat  1 

Kerat  ^ 

Con 

Copo 

Cyst 

Conus 

Contra 

Clonic 


Greek  Color.      (A-chromat-opsia.) 

Greek  Pupil.     (An-iso-corsia. ) 

Greek  Corner  of  the  eye.     (Inner  Canthus.) 

Greek  Down  or  beneath.     (Cata-phoria.) 

Greek  Cornea.     (Ceratometer.)    Proper  Horn. 

Latin  Together  with.     (Convergence.) 

Greek  Strain,  fatigue,  worn  out.     (Copi-opia.) 

Greek  A  sac.     (Dacry-o-cyst-itis.) 

Greek  A  cone.     (Conic  Cornea.) 

Latin  Opposite  .     (Contra  generic.) 

Greek  Pertaining    to     confused     motion.       (Clonic 
Spasm.) 


Disc 

Dys 

Dexter 

Dioptrics 

Diopter 

Dacry 

Edema 

Erration 

Erythro 

Ec,  or  Ek 

Ectos 

Eso 

Em 

Exo 


Greek  A  round  body.     (Optic  disc.) 

Greek  A  prefix  meaning  "Bad".     (Dys-opsia.) 

Latin  The  right.     (Oculus  Dexter.) 

Greek  Science  of  refraction  of  light. 

Greek  A  meter  focus  as  used  in  Optometry. 

Greek  Tear.      (Dacry-ops.) 

Greek  A  swelling. 

Latin  Wandering.     (Aberration.) 

Greek  Red.     (Erythr-opsia.) 

Greek  Out.    (Ec-tomy.) 

Greek  Outside. 

Greek  In.      (Eso-phoria.) 

Greek  A  prefix  meaning  "In".     (Em-metr-opia.) 

Greek  Out.     (Exo-tro])ia.) 


Focus 
Fundus 


Latin 
Latin 


Coming  to  a  point. 
Foundation. 


Graphy 


Greek      Description,  drawing 


Hydro 

Greek 

Hemi 

Greek 

Hetero 

Greek 

Hyper 

Greek 

Hypo 

Greek 

Water. 

Half.     (Hemi-an-opsia.) 
Others,  or  many.     (Hetero-phoria.) 
Over,  above.     (Hyper-phoria.) 
Under,  or  Ijeneath      (Hypo-metr-opia.) 
(My-opia.) 


Kktciium's  Lessons  on  the  Eye 


Words 


Itis 

ISO 

Image 
I  rid 

Greek 
Greek 
Latin 
Latin 

Kinetic 

Greek 

Leuko 
Lachrymal 

Greek 
Latin 

Meter 
Micro 
Megalo 
Mono 

Greek 
Greek 
Greek 
Greek 

Nepho 

Xeuro 

Nyct 

Nebula 

Opia,  Opsia,  Ops. 

Opia 

Greek 
Greek 
Greek 
Latin 

Greek 

Opsia 

Greek 

Ops 

Greek 

Ortho 

Greek 

Oculus 

Latin 

Oma 

Greek 

Photo 

Greek 

Phakia  (phacia) 

Greek 

Plegia 

Greek 

Ptosis 

Greek 

Phobia 

Greek 

Punctus 

Latin 

I^seiido 

Greek 

Phoria 

Greek 

Pyo 

Poly 

Greek 

Pali)ebral 

Latin 

Presby 

Greek 

Rhea 

Greek 

Retina 

Latin 

Spccli'iun 

Latin 

Spasm 

ClriH'k 

Senilis 

Latin 

Sthenic 

Greek 

.Meaning 

Inflammation.     ( Retin-itis.) 

Equal.     (Iso-coria.) 

Resemblance. 

Iris.     Rainbow.      (Irid-o-i)legia.) 

:Motion,  to  move. 

\Miite.     (Leuk-oma.) 

Pertaining  to  tears.     (Lachrymal  ducts.) 

Meter  or  measure,     f  A-metropia.) 

Small.    (Micr-opsia.) 

Large.     (Megal-scope.) 

One  or  single.     (Mon-ocular.) 

Cloud.     (Neph-a-blepsia.) 

Nerve.     (Neur-a-sthenia.) 

Night.     (Nyctal-opia.) 

Cloud,  mist. 

Affixes. 

When  applied  to  a  word  or  a  combination  of 
words,  gives  it  the  meaning  of  "An  error 
of  refraction  vision  which  may  be  cor- 
rected by  glasses",  as  Hyperopia,  Myopia, 
Presbyopia. 

When  ap])lied  to  a,  word  means  "Vision". 
(Chromat-opsia.) 

When  applied  to  a  word  means  "The  eye". 
(Megal-ops.) 

Straight,  normal.  (Orthoporia)  normal 
fixation. 

Eye. 

A  growth  or  new  growth.     (Trach-oma.) 

Light.      (Photo-phobia.) 

Lens.     (Crystalline  lens.)      (A-phakia.) 

Stroke.     (Paralysis.)      (Cyclo-plegia.) 

Falling.     (Blephar-ptosis.)      (Phacia-ptosis.) 

Pear.      (Photo-phobia.) 

A  point.     (Punctum  Proximum.) 

False.     (Pseudo  Myopia.) 

Tendency  to  swerve.     (Hyi)er-phoria.) 

A  prefix  denoting  "Pus".     (Pyo-rrhea.) 

A  prefix  denoting  "Many".      (Poly-coria.) 

Pertaining  toi  the  eyelids. 

Old.     (Presby-o-pia.) 

A  flow  or  discharge.     (Dacry-o-rrhea.) 
A  network  of  sensitive  layers. 

An  appearance.     (Solo-spectrum.) 
Contraction,  cram]).     (Clonic  spasm.) 
Pertaining  to  old  age.     (Arcus  senilis.) 
Strong,  or  strength.     (A-sthen-opia.) 


Ketchum's  Lessons  ox  the  Eve 


89 


Words 

Stigma 
Sclera 
Super 

Staphy 

Scope 

SynechiE 

Sinister 

Sis 


Toxin 
Tomy 
Tome 
Tropia 
Tonic 

Umbra 
Ula 

Vergence 


From  Meaning 

Greek  A  point.     (A-stig-ma-tism.) 

Greek  Hard.     (Scler-o-sis.) 

Latin  Prefix  meaning  "Above"  or  implying  excess. 

(Superior.) 

Greek  A  grape.     (Staphyl-oma.) 

Greek  Observation,  to  view,  viewing.     (Telescope.) 

Greek  Adhesion.     (Blepharo-Synechia.) 

Latin  The  left.     (Oculus  Sinister.) 

Greek  An  Affix.    Action. 

Greek  Poison.     (Toxic  Ambly-opia.) 

Greek  Cutting.     (Irdd-ec-tomy.) 

Greek  A  cutting  instrument. 

Greek  Turning.      (E.xo-tropia.) 

Greek  Continued.     (Tonic  Spasm.) 

Latin  Shadow.     (Umbra-scope.) 

Latin  Small.     (Lentic-ula.) 

Latin  Inclination.     (Convergence.) 


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^  '    Opt.- metrists 


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